Cory tank mates

How about Bolivian Rams? I'm assuming yes to Bolivian Rams as they are not usually aggressive to other non-Rams. They are not usually aggressive full stop in my experience, unless spawning I guess?

Tank is 110 L (25 G). Will be heavily planted. Sand substrate. Plenty of bog wood. x12-16 small albino and bronze Cory. Likely other tank mates, x2 very small BN plecs.

Unfortunately, my London, UK tap water is not very South American river type. pH 7.6 ish, 10 degrees KH and 15 degrees GH.

Hello Alex. You have a small tank. So, whatever you decide to put in it, you'll need to keep the number small and remove and replace half the tank water a couple of times a week.

10 Tanks (Now 11)

10 Tanks said:

Hello Alex. You have a small tank. So, whatever you decide to put in it, you'll need to keep the number small and remove and replace half the tank water a couple of times a week.

10 Tanks (Now 11)

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50% water change twice a week? Not a great hardship, but wasn't banking on it. No argument against 110 L being a small volume of water. Thanks for input.

Hello again. The toxins in such a small amount of water can build up very quickly, even if you have just a few small fish. You can do this. I have 11 tanks that range in size from 45 to 300 gallons and change half the water in each of them every week. The 300 gallon has no filtration, so it generally gets a large water change twice a week. It typically takes 30 minutes per tank to remove and replace half the tank water. You simply need the right equipment and through practice, set up a workable routine.

10 Tanks (Now 11)

AlexTimothy147 said:

50% water change twice a week? Not a great hardship, but wasn't banking on it. No argument against 110 L being a small volume of water. Thanks for input.

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Just to add, the bristlenoses are a high bioload fish. So that makes a good water change routine even more important.

"Aggression" has many facets. Male cichlids are all aggressive, but this plays out differently among species, and sometimes among individuals in a species. It often does not involve physical attacks. But to your initial question, the Bolivian Ram (Mikrogeophagus altispinosus):



Given the tank size here, I would go with a solitary male. As noted above, it feeds from the substrate, and it will if annoyed push Corydoras away from "his" food, as they eat the same things (bug bites, shrimp pellets, frozen shrimp and daphnia). A male will own the tank sapce, without doubt, and all the other fish will know it. But nothing usually proceeds from this, provided the fish are suited to the environment in all respects.

You also want dither fish, for both the ram and the cories. Cories on their own no matter the group size will still feel threatened without fish above them, and this applies to the ram as well. Fish that remain in the upper half obviously, since the ram and cories are lower half. Your hard water makes this a bit difficult, but it is still in my view a necessity.

A comment on water changes...one a week if it is substantial is sufficient, or should be. Live plants, especially floating species, are mandatory for all these fish as none of them like bright overhead light, they feel too vulnerable. There is an article I wrote at the head of the Tropical Discussion forum.

Byron said:

"Aggression" has many facets. Male cichlids are all aggressive, but this plays out differently among species, and sometimes among individuals in a species. It often does not involve physical attacks. But to your initial question, the Bolivian Ram (Mikrogeophagus altispinosus):

Compatibility/Temperament: Peaceful, an excellent cichlid for a community tank of characins, smaller catfish species, rasbora, small loaches, gourami; will co-exist with angels and discus. Fish will sometimes display aggression toward members of their own species including simple chasing, ramming, and lip-locks; while usually non-harmful, targeted fish may be weakened to the point of death. This can apply to mates especially if they did not bond on their own. Best kept as a single fish, or in a bonded pair.​

This species was first imported by Horst Linke and Wolfgang Staeck in 1985, and their reported habitat observations suggest that this species appears to live in solitude (individual fish alone) apart from reproduction periods (Linke & Staeck, 1994). Single fish are therefore good cichlids for a community aquarium. More than one can be housed if the tank provides sufficient floor space for individual territories, and they are introduced at the same time--but peace may not last regardless. The fish remains in the lower third of the water column, spending most of its time browsing the substrate for bits of food.​

Given the tank size here, I would go with a solitary male. As noted above, it feeds from the substrate, and it will if annoyed push Corydoras away from "his" food, as they eat the same things (bug bites, shrimp pellets, frozen shrimp and daphnia). A male will own the tank sapce, without doubt, and all the other fish will know it. But nothing usually proceeds from this, provided the fish are suited to the environment in all respects.

You also want dither fish, for both the ram and the cories. Cories on their own no matter the group size will still feel threatened without fish above them, and this applies to the ram as well. Fish that remain in the upper half obviously, since the ram and cories are lower half. Your hard water makes this a bit difficult, but it is still in my view a necessity.

A comment on water changes...one a week if it is substantial is sufficient, or should be. Live plants, especially floating species, are mandatory for all these fish as none of them like bright overhead light, they feel too vulnerable. There is an article I wrote at the head of the Tropical Discussion forum.

Regular Partial Water Changes

Byron Hosking November, 2010 (rev April 2021) Nothing is more important when it comes to aquarium maintenance than regular partial water changes. The adage “an ounce of prevention is worth a pound of cure” certainly applies here. One frequently reads of products that will reduce the need for...

www.fishforums.net

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Thanks Byron. As of today I have decided to make an attempt to use 25% RO and 75% Tap water. I didn't realise I could get 25 litres of RO for £5 as long as I have my own container. This LFS is a good one. Quite specialised fish room compared to my other LFS and they are only a 25 minute car ride from me. What do you think?

If I get comfortable I could try and push to 50% RO and 50% tap, but for now was thinking 25% RO because my set up is only 110 L (85 L I think with water displacement).

What's the max RO percentage do you think i could use without having to worry about putting minerals into the RO? My tap water is about 7.6 pH, 10 kH and 15 GH.

Re dither fish, my plan was always for tetras. My LFS have a good range. The thing was always some of my LFS keep their tetras in 50% RO. There is another LFS that keeps the following tetras I like in straight tap water, what do you think are the best options below for my set up assuming 25% min RO

- Harlequins
- Black phantom (love these)
- White fin bentosi
- Lemon
- Rummy nose

I actually do not really like the cardinal/neon/glowlight shaped tetras

AlexTimothy147 said:

What's the max RO percentage do you think i could use without having to worry about putting minerals into the RO? My tap water is about 7.6 pH, 10 kH and 15 GH.

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It depends upon the fish. The GH in the water courses in tropical South America is basically zero, or so low as to be zero. I have been fortunate to have such water out of my tap for 30 years. The GH officially is given as close to 7 ppm which is less than half of 1 dH. I do no mineralization because I have always had soft water species. Fish from such water obtain their minerals from what they eat. My plants had more of an issue than my fish, calcium especially, but I solved that with Flourish Tabs (which do not leech into the upper water column) and Flourish Comprehensive Supplement. For you, the question is money, as it would be for me if I had to buy or install RO. Perhaps the latter, long-term, would be less expense?

AlexTimothy147 said:

Re dither fish, my plan was always for tetras. My LFS have a good range. The thing was always some of my LFS keep their tetras in 50% RO. There is another LFS that keeps the following tetras I like in straight tap water, what do you think are the best options below for my set up assuming 25% min RO

- Harlequins
- Black phantom (love these)
- White fin bentosi
- Lemon
- Rummy nose

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None of the listed fish should be in very hard water. A GH of 15 dH is "fairly hard" to use subjective terms. In straight RO they would thrive. They will supposedly manage to some extent with an increase in GH, but I would not like to get into specifics as you might come back on me for killing off your fish over time, lol. Check the GH numbers on Seriously Fish.

The problem with hard water involves how a fish "lives" in its aquatic environment. Water is continually entering the fish's bloodstream as it passes via osmosis through the cells. This is how fish drink. Any substances dissolved in the water that are able to diffuse across the cell membrane (not all dissolved substances can, but calcium and magnesium can and does) thus enter the fish's bloodstream and the fish must deal with them as foreign or toxic substances. In the case of minerals, the kidneys filter out the calcium. In time, the calcium blocks the kidneys and the fish dies. A study in Germany found that the lifespan of cardinal tetras was directly proportional to the level of GH in the tank water; higher GH meant shorter lives. Freshwater fish have evolved over thousands of years to function in very specific water. The extent to which this is said to be adaptable is questionable at best, as some species certainly manage better than others. There are undoubtedly other factors involved.

Of the species listed, looking now purely from where they live in the aquarium water, the harlequins are mid-water, the lemons similar, but the other three are lower level. All your fish will be in the lower half.

Pristella maxilaris do much better in harder water, up to a point. The Penguin Tetras (Thayeria obliqua and T. boehlkei) are surface level and might fare OK here. Ther are some cyprinids suited to harder water, we had a couple threads on these recently. @Wills will remember this better than I can.

Ah you are in my predicament - hard water can be tough to deal with but you can embrace it! At 15 gh you do have some options like Byron said there are some cyprinids that give us great options. Emerald and Galaxy Rasboras, Rummy Nose Rasboras, Red Dwarf Rasboras (I have these) are all great options and in there you have a lot of different colours! Red, blue, green, gold. Rosy Loaches and Inle Loaches are great nano/small tank bottom dwellers (just picked up a bunch myself today). There are a couple of Gourami species that come from Lake Inle that are in the hobby, the Red Honey Gourami and the Thick Lipped if I remember correctly.

A lot of fish from Myanmar, Vietnam and Thailand are good candidates as so much of the landscape is limestone so quite a naturally karstic region - though in the swamps and flooded plains it will soften but in the open streams the fish will interact with a certain degree of hardness that would make me comfortable keeping them in harder water like ours.

Krabi Province in Thailand is an other interesting one - home to Betta Simplex, Croaking Gourami and Espi Rasboras super super hard water due to the limestone substrates the lakes flow through and again some common species - though we've previously debated if these are fair assumptions that all strains of these species can deal with hard water, though my conclusion is that it is fair, nearly got some Espi today but went for the Rosies.

But... my over arching advice for anyone with hard water - go Rift Lakes. Tanganyika gives you a lot of options in this size tank, things like Shell Dwellers and some Rock Dwellers Caudopunks are very nice and so are Daffodil Cichlids and Fairy Cichlids, small group of Synodontis Petricola or Lucipinnis to go with them and maybe some Goby Cichlids if you can find them. But if you have a footprint of 3 foot x 1 foot in your tank a small colony of Chindongo Saulosi would be comfortable. Black and blue striped males with bright yellow females get to 3-4 inches and you could probably have a trio of Synodontis Petricola in there with them to help keep on top of fry.

Wills

Thanks @Wills and @Byron will read up and come back to you

Byron said:

Check the GH numbers on Seriously Fish.

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Thanks for explaining about the impact on the fish when they are in hard water and built for soft water. Especially with their kidneys and reduced life expectancy.

On Seriously Fish, these are the figures that are coming back. I do understand that most likely, the upper range of hardness such as 15 for a Bronze Cory and 12 for a Lemon Tetra does not mean optimal conditions for that fish, and most likely we are to aim for somewhere in the middle of the range as the ideal max hardness? Such as 8.5 for a Bronze Cory and 6.5 for a Lemon Tetra?

From Seriously Fish (the brackets) are me converting ppm to degrees German hardness as Seriously Fish use ppm.
Bronze Cory pH: 6.0 – 8.0 Hardness: 36 – 268 ppm (2-15)
Black Phantom Tetra pH: 5.0 – 7.0 Hardness: 18 – 215 ppm (1-12)
Harlequin pH: 5.0 – 7.5 Hardness: 18 – 215 ppm (1-12)
Ornate Tetra (White fin) pH: 5.0 – 7.5 Hardness: 18 – 215 ppm (1-12)
Lemon Tetra pH: 5.0 – 7.5 Hardness: 18 – 215 ppm (1-12)
Rummy Nosed pH: 5.5 – 7.0 Stated as 2-15 Degrees Hardness

I've tested the results of 40 litres of water this evening. That was 50% my tap water and 50% the RO water I collected today.
pH 7.5
Carbonate hardness 6 degrees (German)
General hardness 9 degrees (German)
I'm guessing my 50/50 RO/TAP pH has barely dropped from 7.6/7.8 to 7.5 because my tap water is 10 degrees carbonate hardness? If i did stick to 50/50 tap/RO could my pH actually be a bigger problem for tetra's than my hardness?

I will pick apart @Wills post tomorrow about alternatives to Tetra's for my set-up. I will deffo be getting dither fish, one way or the other.

Also, I wanted to ask you a more philosophical question Byron, about these tetra's I like maybe being better off with me than someone else.....

In my LFS options (there are about 3 quite nice one's all in close proximity). One of the LFS state they use 50% RO with their tetra's, the other LFS states they use about 25% RO, and the other LFS use no RO with their tetra's, just 100% tap. I know that a great majority of the people I see buying tetra's in any of these LFS are unlikely to have RO at home. These LFS are close enough to where I live to most likely have very similar hard and alkaline tap water such as myself.

Often in the LFS, it's a case of a child saying "Mummy I like these fish" and they are Cardinal, or Neon Tetra's and the LFS can't fish them out 4 fish for £10 quick enough. I know for sure, with some of the tetra's I like, I could give them a better life than perhaps 75% of the people buying tetra's in that LFS. This makes me more determined to keep the door open to having some tetra's in my set-up, BUT... I have not decided for sure, because the case against them in my set up is quite compelling as well to be honest.

Some pictures of my old planted up community tank. Check out the female Convict. I had convicts breeding in other tanks. This female was as good as gold in the community tank for over a year. Just her, as her husband was trying to murder her in the convict set-up. Domestic abuse.

Byron, for a bonus point, find my Bolivian Ram in these pictures!

The Bolivian is over at the far right in the last photo.

With soft water species, there is certainly no doubt that they will be healthier, longer-lived and less prone to problems if they are in very soft water. But we do what we can.

The proportion of tap and RO at 50/50 should reduce the GH by half. The pH will lower probably, but the KH as you say will buffer it. But your numbers are not at all bad here.

With fish stores, it doesn't really matter what they do if this is not continued by you after acquisition. Fish are in fish stores for brief periods (hopefully) and most have no issues short-term. But long-term to the fish's life's end is a very different matter.

I would never acquire a fish to prevent someone else giving it a less-than-satisfactory home. This occurs here on the forum.

@AlexTimothy147 I suffer from the same water you have in London (only harder and full of nitrates). For my SA tank which has only Cories, tetras and pencilfish I use straight RO water with no issues. Its the tank in my signature. As long as you keep easy plants they will be fine with what is produced by the fish, fish food and and minimal ferts, I use TNC lite or Flourish Comprehensive. My fish are also very much brighter (in colour) than when I was using tap water.
Check out spotlesswater.co.uk if they have a self service location near you it is much cheaper than using your LFS. I do have my own unit because I use around 200l / week (for 4 tanks) and that is a pain to lug around.

FWIW my Bristlenose made it to 19 years in this tank - although he had tap water for about the first 75% of his life.

seangee said:

@AlexTimothy147 I suffer from the same water you have in London (only harder and full of nitrates). For my SA tank which has only Cories, tetras and pencilfish I use straight RO water with no issues. Its the tank in my signature. As long as you keep easy plants they will be fine with what is produced by the fish, fish food and and minimal ferts, I use TNC lite or Flourish Comprehensive. My fish are also very much brighter (in colour) than when I was using tap water.
Check out spotlesswater.co.uk if they have a self service location near you it is much cheaper than using your LFS. I do have my own unit because I use around 200l / week (for 4 tanks) and that is a pain to lug around.

FWIW my Bristlenose made it to 19 years in this tank - although he had tap water for about the first 75% of his life.

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Oh wow. Going to read up on spotlesswater later and get back to you

AlexTimothy147 said:

Oh wow. Going to read up on spotlesswater later and get back to you

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My bf is a window cleaner and uses spotless water, it's pretty reasonable if you have one near you (I don't use it for my tank as I'm not experienced enough and worry I'd mess it up but maybe one day!)