Pygmy Corys in Hard Water?

[JackGulley]

The seriouslyfish website does not have a page for normal otos. Other sources I have found just say not to go above 8 dGH, which is exactly the same as the Cories and exactly what my tank is currently at. I can also easily reduce the amount of crushed coral to bump it down a tad so it's not right on the edge of the preferred range.

 

[AdoraBelle Dearheart]

That website doesn't have a page for the common oto. For an obscurer species of oto, the only one it describes, it gives a hardness range of 36-179 ppm, which my tank water is well within.

I'm a huge fan of otocinclus too, and have kept them for a few years now, read and researched a lot about them, and learned from my own mistakes too. One of my main fishkeeping dreams is to successfully breed otos - they're not easy to breed in captivity, although it's been done- but mostly in small numbers by lucky hobbyists, not enough to meet the demand for them, since they're popular as tank cleaners. But it means that the any you see in in store tanks are wild caught, and I'm afraid they go through a terrible time being caught, shipped, and the death rate for an oto shipment, and when people bring them home to their tanks, is incredibly high.


The reason it's hard to find a range for "common oto" is because there isn't really such a thing. There are several subspecies that are usually all just sold as "otos", and the shipment/store tank often contains a mix of those species, that are very similar looking, and you need to look closely and know the differences between their markings to know which sub-species you have, that have all been labelled and sold as common otocinclus. So it can get a bit confusing! When I learned this, I watched my otos for ages, checking and re-checking the marking differences, and discovered I had a mix of the three most common sub-species. No wonder they didn't breed! But they're social fish that live in groups of thousands in the wild, and still appreciate being in a group, and it's almost impossible to source specific common sub-species when they're generally caught, chucked into huge warehouse containers all mixed together, then bagged and shipped around the world, many dying in transit, in the store, or if they survive all of that, then often are weak and starving by the time they get to a home tank. If that home tank is a brand new set up, and the wild caught otos aren't yet acclimated to eating commercial food, or even offered it, people often lose a lot of the otos they only just bought too.

So it's well worth knowing these things in advance, so you can prepare properly before getting these charming and undervalued fish!

I think you could have a group of otos in that water, especially if you stop hardening it, lean towards softwater for both the pygmies and otos, and especially if you're willing to add botanicals like oak or almond leaves, alder cones etc, driftwood. These add tannins to the water, which some people (like me!) like, help soften the water, and encourage microcritters that work on breaking down the botanicals, and otos love to graze on biofilm and I'm convinced also eat some of those micro-critters as they graze, not solely algae eaters. Although making sure you let the tank mature and get properly established, adding plenty of live plants, and leaving soft green algae and biofilm to grow on at least the back pane of the tank so they can graze and have a food source before you get them, all helps! Gives them a better chance of making it.

Seriously Fish does give that range for the Zebra oto - that one isn't sold as a common oto since it's so visually distinct, being striped and larger, so sells for more money. https://www.seriouslyfish.com/species/otocinclus-cocama

It also has this profile for one of the more commonly sold sub-species that are often sold as common otos: https://www.seriouslyfish.com/species/otocinclus-macrospilus/
Hardness: 1-12°H

So I think a group of otos could work really well for you You'd be near their upper range for hardness, and ideally, they like it on the softer end, but I also keep some fish that are at the higher end of their range, but still within range, so I don't see anything wrong with that. Just have to accept that they're unlikely to breed in that hardness, and if able and willing, aim to learn towards a softwater tank, rather than hardening it as you have been.

 

[AdoraBelle Dearheart]

Had more to add, but wanted to reply soon since I can see how much you want the pygmies and otos, and also want to say that they go really well together! For example, in the wild, specific species of oto are usually found near and in the same areas, mixing with, specific types of cories. Ones with similar markings. Researchers believe that this is likely a safety mimic adaptation. Not only is there safety in numbers, and otos and cories both live in huge groups in the wild, and are very social with each other, needing to be with conspecifics to be happy, but both cories and otos are peaceful, non-aggressive and not territorial fish.

Otos have nothing really in the way of defences. Just speed and the ability to hide and blend into the background if a predator is around. However, corydoras have both a toxin, and sharp barbs in their dorsal and pectorial fins, which can make a predator very wary of attempting to eat them! Those sharp barbs can do some real damage, as any fish keeper that's been spiked by them can attest!

The otos may also benefit from this wariness by being around similar looking cories, and mistaken for a cory by a predator.


My otos will often swim along witg and follow the group of pygmy cories when they're all active, or vice versa. They live well together, so I like that you want both!

However, the downsides... the platies might be better off being re-homed... however, if the water is still within their range (I haven't checked), then there may be no point in rehoming them, since the people close to you will likely be keeping them in the same water range you have! If it's out of their range, and you want to keep them, then maybe just accept that they are not likely to live as long in softer water than they would in hard, or perhaps set up another tank and harden up the water for the hard water species in that one? It is at least, much easier to harden up soft water, than it is to soften hard water!

I don't know and haven't checked the GH ranges for WCMM and zebra danios. But I've kept the latter, and familiar with the former, and the bad news is that I don't think they'd work well with the pygmies or otos. If you're willing to return or rehome those, I think you'd have a better chance of success with the pygmies and otos.

Reasons being that both are very fast and agile swimmers, move around constantly with a lot of frenetic energy, and voracious eaters, that will both spook the much shyer and easily spooked otos and pygmies, leading them to hide away more, and the danios and WCMM will quickly snap up the food you add, so could easily out-compete the cories and otos for food.

So I'd really give the tank stocking a re-think, and plan it with the otos and cories in mind, since you seem really drawn to and set on them! Then if you're willing to let go of, or set up other tanks for, the platies, danios and WCMMs (and WCMM's are subtropical/cooler water fish anyway, so would be better off returned or rehomed I think, so you can keep the tank a bit warmer for the other species), you'd have a huge variety of other softer - middling water species that would work brilliantly in the upper levels of the tank, are also peaceful and not likely to scare or out compete the shy cories and otos.

Seriously, there are some wonderful and stunning species we can suggest, and there's nothing wrong with changing things up as you learn more, and can then plan a set up that works for all the inhabitants, works with your source water, and makes you happy! We'd be very happy to help with suggestions for other upper level fish, or a second tank set up if you wanted to go that route.

 

[JackGulley]

Thank you for giving me so much advice! That interaction of the pygmys and otos sounds really cool! I don't have interest in setting up a second tank rn as this is my first tank, but it looks like if I keep the hardness around 8 dGH all the fish will be healthy. Advice taken for the danios/minnows being aggressive, I was already considering replacing them with something else. I'm excited to go get the cories and otos later today!

 

[Seisage]

Thank you for giving me so much advice! That interaction of the pygmys and otos sounds really cool! I don't have interest in setting up a second tank rn as this is my first tank, but it looks like if I keep the hardness around 8 dGH all the fish will be healthy. Advice taken for the danios/minnows being aggressive, I was already considering replacing them with something else. I'm excited to go get the cories and otos later today!

Tip for picking out healthy otos: look at their bellies! They should have nice, large, round bellies that look almost like a little pearl. That'll let you know that they're eating well in captivity. Also make sure to ask the LFS owners how long they've had the otos, what they've been feeding them, etc. and make sure to watch the fish and get a good look at the tanks in general.

If the otos are a bit skinny, proceed with caution. Don't get otos that are emaciated. If the LFS just got the otos in recently, maybe hold off for a bit and wait until the otos at the shop are more settled. Ask if your LFS can place holds on fish for you. If the tanks at the LFS are super clean with no biofilm, and they don't otherwise feed the otos, I don't think I'd personally buy from them.

Good luck! Hopefully the ones at your LFS are nice and healthy. As always, quarantine them at home if you can, to avoid spreading diseases to your current fish.

 

[AdoraBelle Dearheart]

Thank you for giving me so much advice! That interaction of the pygmys and otos sounds really cool! I don't have interest in setting up a second tank rn as this is my first tank, but it looks like if I keep the hardness around 8 dGH all the fish will be healthy. Advice taken for the danios/minnows being aggressive, I was already considering replacing them with something else. I'm excited to go get the cories and otos later today!

You're most welcome!

The danios and WCMM aren't aggressive, as such. But their frenetic energy, and the ease with which they'd snap up all the food you add - will spook and out-compete the cories and otos easily, so I personally wouldn't stock them together.

I also wouldn't run out and buy both pygmy cories and a group of otocinclus today - otocinclus also need a group of 6-8, so that's a lot of fish you'd be adding in one go, and without returning/rehoming any other fish either, you're at risk of overstocking the tank, and causing an ammonia spike if you add them all at once, and are trying to get enough food to the lower level for the otos, potentially increasing waste even further...

SLOW DOWN. The key to this hobby is patience. Get your pygmies today since you've already ordered them, let the tank bacteria adjust to the added bioload and let them settle in, observe how they do as they settle in, especially as they compete for food with the zebra danios and WCMMs.

Otos should be added last, especially after you've encouraged microcritters and algae to grow, and all new stock should ideally be quarantined, with wild caught like otos treated for internal parasites.

You're rushing, and your tank isn't ready for that yet.

 

[JackGulley]

Cories and otos are now in the tank! LFS sadly only had 2 Otos, but I will get more so they aren't stressed. It's very fun to watch the cories school. I expected the danios to be nipping them because they're usually kinda mean, but the cories actually keep going to investigate the larger as a little school, with the danios awkwardly trying to avoid them. Unfortunately the danios and platys pigged out on the algae wafers while I wasn't looking


The tank they're going in

Two cories and an oto (not sure why the pictures turned sideways)

Oto

Cory on a leaf


I did do a water change a few days ago, and I added Stability since I'm adding more bioload. I will figure something out for feeding.

Edit: There's already diatoms on the glass and rocks but I'm going to try to keep the lights on longer to grow more algae

 

[JackGulley]

I will be monitoring for any ammonia spikes.

 

[AdoraBelle Dearheart]

Corydoras needs more protein than algae, they're insect eaters in the wild. Bug Bites is one of the best foods you can give them, the smallest are the microgranules, but I still have to crush those even smaller to feed the pygmies.

Other good foods for Corydoras, especially the tiny ones like pygmies, are smaller live or frozen insects. Cyclops, daphnia, moina, baby brine shrimp, microworms, walter worms, banana worms - I buy a variety of frozen foods to feed mine, both the large and the smaller cories, and they get Bug Bites as a dry staple food. Algae wafers are only an occasional treat for them, although they do all enjoy an algae wafer now and then, don't overdo it, since it shouldn't be a mainstay of their diet.

However, especially in a new, clean tank as this looks to be, you might need to add algae wafers now and then to suppliment the otos... if algae wafers can get past the greedy livebearers, danios and minnows, and aren't then devoured by the cories, and it can take time for wild caught otos to get the hang of accepting commercial foods as well. Have heard plenty of examples of otos starving to death in a tank where algae wafers were on offer, but the otos hadn't yet figured out it was food. Remember that they're wild caught, and not raised on commercial foods.

Well, what's done is done, so congrats on your new fish, but please don't buy more otos for a long while. Not until you're sorted out the stocking in the upper levels, and have got a solid grip of the dietary needs of the cories and the otos, and you're sure you're able to feed both.

I'd also add a black background, or any background that's solid, to the tank, so the fish feel more secure, and the colours and plants will visually "pop" better against a black background too. Then invest in more plants, and more hardscape that the cories can hide in, explore, and sit on. They like to sit around on things, and they like to feel safe. Oddly, the more hiding places shy fish have available to them, the more you see them out in the open.

Allow soft green algae to grow (otos won't eat pest algae like hair, BBA, or staghorn), and you can also culture algae on smooth river stones placed in a bowl in a windowsill. Keep an eye on whether the otos tummies are rounded when they're on the glass. They should always have a round little tummy, otherwise, they're starving.

Dropping an algae wafer in an hour or two after lights off, when the upper level fish are asleep, will give the otos a better chance of getting to it.

Wait to see how this works out before adding more otocinclus. please. They're a wonderful fish that deserve the proper care, diet, tank set up and research before being bought home.

 

[Seisage]

I agree with Adora, here. You're going to need to play a very difficult game of catch-up here in terms of figuring out feeding and monitoring water quality. I'd keep an eye on that cloudy water. Many softwater/blackwater fish like corys and otos don't tolerate bacteria blooms well. This is usually solved by over-filtration.

As for feeding, I can't speak much to the corys, but for otos, your tank definitely looks too clean for them to thrive without supplemental feeding. They really need a LOT of biofilm. Algae wafers are a good starting point, but as Adora mentioned, most otos are wild-caught and may not take to commercial foods easily. You can also try blanched or boiled zucchini or cucumber, as well as Repashy Soilent Green. I've heard many good things about the Repashy gel food line and that otos really like the soilent green variety.

Do you have any pictures of the otos' bellies? The belly is definitely the best way to tell condition, but I can already tell you that the one that we have a side view of definitely looks skinny. Otos do have larger head proportions than other fish, but that fish is mostly head. That is, the body has little mass on it. You need to get them to eat ASAP. I've heard of people purchasing emaciated otos that don't end up eating even if they have food available because they're just too far gone at that point.

 

[JackGulley]

Corydoras needs more protein than algae, they're insect eaters in the wild. Bug Bites is one of the best foods you can give them, the smallest are the microgranules, but I still have to crush those even smaller to feed the pygmies.

Other good foods for Corydoras, especially the tiny ones like pygmies, are smaller live or frozen insects. Cyclops, daphnia, moina, baby brine shrimp, microworms, walter worms, banana worms - I buy a variety of frozen foods to feed mine, both the large and the smaller cories, and they get Bug Bites as a dry staple food. Algae wafers are only an occasional treat for them, although they do all enjoy an algae wafer now and then, don't overdo it, since it shouldn't be a mainstay of their diet.

Noted.

However, especially in a new, clean tank as this looks to be, you might need to add algae wafers now and then to suppliment the otos... if algae wafers can get past the greedy livebearers, danios and minnows, and aren't then devoured by the cories, and it can take time for wild caught otos to get the hang of accepting commercial foods as well. Have heard plenty of examples of otos starving to death in a tank where algae wafers were on offer, but the otos hadn't yet figured out it was food. Remember that they're wild caught, and not raised on commercial foods.

Well, what's done is done, so congrats on your new fish, but please don't buy more otos for a long while. Not until you're sorted out the stocking in the upper levels, and have got a solid grip of the dietary needs of the cories and the otos, and you're sure you're able to feed both.

I'd also add a black background, or any background that's solid, to the tank, so the fish feel more secure, and the colours and plants will visually "pop" better against a black background too. Then invest in more plants, and more hardscape that the cories can hide in, explore, and sit on. They like to sit around on things, and they like to feel safe. Oddly, the more hiding places shy fish have available to them, the more you see them out in the open.

I had actually been using a black background that I made of construction paper, but I dropped it in the water and didn't replace it because I'm going to buy a real one instead.

Allow soft green algae to grow (otos won't eat pest algae like hair, BBA, or staghorn), and you can also culture algae on smooth river stones placed in a bowl in a windowsill. Keep an eye on whether the otos tummies are rounded when they're on the glass. They should always have a round little tummy, otherwise, they're starving.

Dropping an algae wafer in an hour or two after lights off, when the upper level fish are asleep, will give the otos a better chance of getting to it.

Wait to see how this works out before adding more otocinclus. please. They're a wonderful fish that deserve the proper care, diet, tank set up and research before being bought home.

I would like to try to borrow an algae-covered rock from someone's more mature tank in order to introduce the algae species. I am worried about the otos eating, especially because they haven't noticed the algae wafers. Do you think they would figure it out quicker if I placed them on a leaf instead of on the substrate? They don't really go on the ground at all, just cling to the wall, rocks, and plants.

I agree with Adora, here. You're going to need to play a very difficult game of catch-up here in terms of figuring out feeding and monitoring water quality. I'd keep an eye on that cloudy water. Many softwater/blackwater fish like corys and otos don't tolerate bacteria blooms well. This is usually solved by over-filtration.

The water is cloudy in that picture because I had just rescaped the tank and there was dust from new rocks. Its clear now.

As for feeding, I can't speak much to the corys, but for otos, your tank definitely looks too clean for them to thrive without supplemental feeding. They really need a LOT of biofilm. Algae wafers are a good starting point, but as Adora mentioned, most otos are wild-caught and may not take to commercial foods easily. You can also try blanched or boiled zucchini or cucumber, as well as Repashy Soilent Green. I've heard many good things about the Repashy gel food line and that otos really like the soilent green variety.

Glad to hear that otos like repashy food; I'm already planning to switch to that soon because I think it will be better for all the fish.

Do you have any pictures of the otos' bellies? The belly is definitely the best way to tell condition, but I can already tell you that the one that we have a side view of definitely looks skinny. Otos do have larger head proportions than other fish, but that fish is mostly head. That is, the body has little mass on it. You need to get them to eat ASAP. I've heard of people purchasing emaciated otos that don't end up eating even if they have food available because they're just too far gone at that point.

They both look like this.

Edit: I also tested for ammonia this morning, no problems so far

 

[AdoraBelle Dearheart]

Noted.

I had actually been using a black background that I made of construction paper, but I dropped it in the water and didn't replace it because I'm going to buy a real one instead.

I would like to try to borrow an algae-covered rock from someone's more mature tank in order to introduce the algae species. I am worried about the otos eating, especially because they haven't noticed the algae wafers. Do you think they would figure it out quicker if I placed them on a leaf instead of on the substrate? They don't really go on the ground at all, just cling to the wall, rocks, and plants.

The water is cloudy in that picture because I had just rescaped the tank and there was dust from new rocks. Its clear now.

Glad to hear that otos like repashy food; I'm already planning to switch to that soon because I think it will be better for all the fish.

View attachment 335545
They both look like this.

Edit: I also tested for ammonia this morning, no problems so far

Yes, I'm sorry to tell you, that oto is starving, underweight, and they both may not make it I'm afraid. If they haven't eaten in the warehouse after being caught (and the suppliers who catch them do tend to throw in algae wafers or similar, but not nearly enough for the hundreds -thousands of otos they've caught, and as you've noted with yours, not all will immediately recognise it as being food either, because they're wild caught fish, not raised on commercial foods.

Then they're shipped, which can take a few days, go into clean store tanks, and many have died by this point, and in the store. So by the time you've got them to your home tank, if the store hasn't managed to get them to eat either, they're already emaciated and in a bad way. If the new tank is well prepared for otos, with lots of soft green algae, plants, biolfilm on driftwood, broken down leaves etc, the otos have a much better chance of finding food within the tank, recovering and regaining weight, and gradually getting used to commerical foods

This is why we tried to encourage you to research and wait first, before running out and getting them. Now you've bought some otos that were already starving, and your tank isn't set up to give them a chance to recover, and you may not have enough time to find things they can and will eat, and it may already be too late for these two, even if you had a perfectly prepared tank.

I don't want to be harsh on you, believe me! This is your first tank, we all make mistakes in our tanks, especially when new to the hobby and it's our first tank, and we get carried away in our own enthusiasm. But espcially for delicate fish like these, and they're famous in the hobby for how difficult it can be to get a surviving group, because of all the above mentioned things they go through before we buy them, and how often they land up in a spanking new clean tank, with nothing natural for them to eat.

Best advice I can give now, is to go back to the store, or any fish store, today, and buy some Repashy Soilent Green. You need it ASAP, call ahead to check if they have it, and you can't afford to wait for an online order, even another few days could make the difference between life and death for these fish. Also get different brands of food for algae eaters, a piece of driftwood, and as many live plants as you can afford to get.

Driftwood will develop biolfilm once added to the tank (go for mopani, or similar, which will add tannins and develop biofilm), and if they have them, some botanicals too, like almond leaves, or whatever they have. The live plants will also have biofilm and microcritters, and potentially algae, and hopefully help to feed them. Leave the lights on for a much longer photo period, and even better if the tank is near a window, leave the window uncovered to encourage algae growth on the tank glass, while also leaving the tank lights on for much longer, also to encourage algae growth.

Try also asking on local FB groups for help from local hobbyists. Explain you have these otos, they're starving, can anyone spare some algae covered stones/gravel/plant trimmings, anything that otos can feed off. If you were local to me, I'd happily spare some things to try to save these little guys, and hobbyists can be helpful and generous in a crisis like this.

 

[JackGulley]

I'm getting an algae-covered piece of wood from a mature tank this afternoon, and the repashy gel food comes tomorrow (unfortunately neither my local LFS nor Petsmart carry it, but we can get next-day shipping). In the meantime, I blanched a couple of cucumber slices and put them in there, but the otos don't seem to notice them. I'm about to try some lettuce instead, since they already know to eat off of the leaves of the plants. At the very least, I believe they are finding SOME algae in my tank as well. They didn't investigate the cucumber because they were busy eating on the plants and rocks.

 

[AdoraBelle Dearheart]

Good luck, I hope they do manage to pull through and make it! I'd be really happy to hear that.

Please will you keep us updated, either way?

When you get the repashy, you can mix some in an open container, then dip things like the top of a pleco cave, some stones, a bit of wood - anything long, in the mixture, and it'll set like a gel onto whatever objects you're dipping. This allows more surface area, and is ideal for plecos and otos, giving them a long surface, or more surface area on stone etc, where they can graze as they would in the wild.

Also gives them a better chance against the top level fish. Again, I'd recommend doing this especially after feeding the upper level fish, and after lights out, so they stand a better chance of getting at it before the others do. But in t this case, put it in asap.

A different note of caution - while it's urgent to get different types of food in there that they may eat, be careful to remove uneaten food ASAP. Uneaten food very quickly begins to decompose in the water and release ammonia - algae wafers often do this fast, and it's easy to cause an ammonia spike. So daily gravel vac-ing out uneaten food is important, and removing uneaten veg within 6 hrs or so.

 

[TwoTankAmin]

Lava rock covered with Repashy Soilent Green.