cory problems

[WhistlingBadger]

Hi, all. I have terrible luck with cories. I have a 150g tank with a sand substrate, heavily planted and aquascaped. There is usually a lot of mulm on the bottom, but the water is extremely clean--it's very rare that tests show any detectable nitrate, and never any nitrite or ammonia. I do a 20 to 50% water change at least a couple times a month. Great, right?

Well, it is...except for my cories. They don't do well. Most of them don't survive, and those that do tend to lose their barbels. I want to order some more, but not until I figure this out and can give them what they need. Any ideas what is going wrong?

 

[Slaphppy7]

Hi, all. I have terrible luck with cories. I have a 150g tank with a sand substrate, heavily planted and aquascaped. There is usually a lot of mulm on the bottom, but the water is extremely clean--it's very rare that tests show any detectable nitrate, and never any nitrite or ammonia. I do a 20 to 50% water change at least a couple times a month. Great, right?

Well, it is...except for my cories. They don't do well. Most of them don't survive, and those that do tend to lose their barbels. I want to order some more, but not until I figure this out and can give them what they need. Any ideas what is going wrong?

I have the exact same experience, with the same tank conditions that you have, when dealing with corys...I've given up on them

I have no clue why they don't do well in my tanks, while the rest of my fish thrive...other bottom dwellers (plecos, shrimp, snails, and occasionally otos) do just fine...it's a mystery to me

 

[WhistlingBadger]

I have the exact same experience, with the same tank conditions that you have, when dealing with corys...I've given up on them

I have no clue why they don't do well in my tanks, while the rest of my fish thrive...other bottom dwellers (plecos, shrimp, snails, and occasionally otos) do just fine...it's a mystery to me

Well thanks for the emotional support.

 

[Naughts]

Which sand are you using?

 

[WhistlingBadger]

Which sand are you using?

Washed play sand from the hardware store.

 

[Akeath]

There is usually a lot of mulm on the bottom

That is your problem. Despite Corycats being sold as bottom cleaners, they actually do really poorly in tanks with dirty substrates. They get barbel infections (which is likely why they're losing their barbels) and can die. For my Corycats, I do 40% weekly water changes with thorough gravel vacuuming. If there's visible mulm on the substrate, it's too dirty and you need to vacuum clean more often/more thoroughly. You can also get extra mulm on the substrate if you aren't making sure your filter tubes are clean enough for things to go through easily and if you aren't occasionally cleaning your filter media in tank water in a container outside of the tank to make sure everything is flowing well. If the filters are too full of detritus they may not suck up anymore, leaving you with lots of mulm on the bottom of the tank. You might also want to make sure your filter intake isn't really high up on the tank, too, to ensure it can suck up detritus from the bottom.

Another common cause of death with Corycats is starvation. A lot of the other bottom dwellers you mention are algae eaters that may be getting part of their diet from algae in the tank. Corycats aren't algae eaters, though, so algae in the tank won't help to sustain them. They'll need to be fed specifically with sinking food for omnivores. Feeding enough food for the upper water fish for the Corycats to have leftovers leaves the substrate too dirty. Instead you should lower the amount you feed your top dwellers till there isn't leftovers, and add some sinking omnivore wafers for the Corycats - enough that after 2-3 hours the Corycats have gobbled it all up. I say 2-3 hours because sometimes sinking wafers take hours to soften enough to eat so the upper water fish don't get it all before the Corycats can. Even with the sinking food, don't feed so much that the substrate is visibly dirty all the time.

 

[Byron]

What exactly is the "mulm" on the substrate? I had 40 Corydoras in a 40g tank and I never touched the sand because it was spotless.

Water changes should be more often, once a week. My cories really appreciated the water change, they were out within minutes charging around the sand. Spawning activity was frequent especially after the W/C.

Barbel loss is usually due to either rough substrate or bacteria in the substrate. Roughness should not be the issue here, if you used Quikrete Play Sand (assuming you are in NA). Argos Play Sand available in the UK is also safe according to members. This brings us back to the "mulm" problem.

Something else may be related here...what foods are you feeding for the cories?

 

[WhistlingBadger]

By mulm I mean brown gunk that accumulates on top of the sand. I assume it's mostly fish waste, as the fish generally aren't overfed.

Feeding: They get high-quality cory pellets (I forget the brand), which they seldom touch. They mostly seem to enjoy foraging about looking for tidbits. I only have three cories currently, so it's hard to get food down to them without overfeeding, if that makes sense. I know they need more company, but I don't want to buy more unless I can be reasonably sure that they'll be OK.

A couple of complicating factors: First, I am extremely limited in my ability to vacuum the sand because this is a heavily scaped tank and the python just won't reach a lot of places. Also, this tank is not in my home; I keep it for a business client. This makes things like frequent water changes and specific feeding regimens a challenge. But the lady that runs the office is a fish enthusiast, so if there are specific recommendations I'm sure we can get it done.

 

[Deleted member 149562]

Personally I would get rid of the mulm. It could well be harbouring the cause for the lost barbels and its likely causing a block to the Cory's love of sand sifting and digging

They are only little and having to shift mulm before they can get to the sand underneath is going to be hard work for them....and rotting poo and other muck from plants etc is not going to be healthy for those little noses and barbels

Try and clear as much of the mulm as you can, expose the sand and give it a good puffing with a turkey baster which will help release noxious nasties and get the sand softer and easier for their noses to sniffle and snuffle in

 

[Byron]

Agree, the mulm might be the source of bacteria that causes barbel loss. I had something like this in my 29g tank with pygmy cories, so I ran the water changer over the open sand to remove it, thinking it might be a problem if not. Whereas in the 40g tank with 40 cories, I never had to clean the sand. Each tank can be different for various reasons.

Bug Bites is the food to use here. The cories will find every last one if it sinks. And upper fish love them too. Bug Bites is one of the most healthy and nutritious foods because it contains soldier fly larvae, and all fish we keep (aside from the herbivores) eat insects and insect larvae as their primary food in the wild, so you cannot do much better. Frozen daphnia is a close second.

 

[WhistlingBadger]

Personally I would get rid of the mulm. It could well be harbouring the cause for the lost barbels and its likely causing a block to the Cory's love of sand sifting and digging

They are only little and having to shift mulm before they can get to the sand underneath is going to be hard work for them....and rotting poo and other muck from plants etc is not going to be healthy for those little noses and barbels

Try and clear as much of the mulm as you can, expose the sand and give it a good puffing with a turkey baster which will help release noxious nasties and get the sand softer and easier for their noses to sniffle and snuffle in

There is lots of exposed sand. There's no way I can remove all of it, as it's a very large tank with lots of woodwork, but I do pull out what I can by hand. Maybe this tank just isn't meant for cories. Maybe time to start thinking about alternatives.

Agree, the mulm might be the source of bacteria that causes barbel loss. I had something like this in my 29g tank with pygmy cories, so I ran the water changer over the open sand to remove it, thinking it might be a problem if not. Whereas in the 40g tank with 40 cories, I never had to clean the sand. Each tank can be different for various reasons.

Bug Bites is the food to use here. The cories will find every last one if it sinks. And upper fish love them too. Bug Bites is one of the most healthy and nutritious foods because it contains soldier fly larvae, and all fish we keep (aside from the herbivores) eat insects and insect larvae as their primary food in the wild, so you cannot do much better. Frozen daphnia is a close second.

Bug Bites. I'll see if I can find some. Even if I don't have cories, my other fish will love it.

 

[WhistlingBadger]

Also: Black soldier flies are kind of cute.

 

[Deleted member 149562]

How often do you puff the sand with a turkey baster?

Pockets of noxious nasties under the surface from rotting poo and leaves etc will poison anything that digs or sifts the sand like Cories

 

[Slaphppy7]

Bug Bites. I'll see if I can find some. Even if I don't have cories, my other fish will love it.

My fish devour them...there's both flake and pellet forms

 

[Deleted member 149562]

A turkey baster will also gently clean the sand around wood, plants etc...so not just getting rid of nasty gases under the surface but helping to tidy up where the usuall cleaning equipment cannot reach

Buy the biggest available....Fluval also do them too, their largest is 18" long.