Bristlenose & clown loaches killing/eating corydoras?

[Yarkii]

Hello!

I've had 5 Julii corydora cat fish for at least a year in my tank, as well as livebearers. Over time I've also brought in some bristlenose catfish and a clown loach. More recently I introduced 5 peppered cory catfish, a couple of extra bristlenose catfish and 2 more clown fish. Since then, my juliis and peppers have been dying, one after the other, and the bodies being eaten by the bristlenose.

Is it possible that the bristlenose or the catfish are killing the corys for food?

TIA


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[mikey11]

how big is your tank?

 

[Byron]

Yes, what is the tank dimensions?

To answer your question, the Bristlenose will not kill cories that are healthy. They will feed on any dead fish, most fish will, so that is likely what you are seeing.

The clown loach might kill the cories, but from the little you have told us so far I would be more likely to suspect some pathogen was introduced with the new fish. Please give us more detailed information on this tank, the fish, when added, etc.

 

[Colin_T]

your fish are dying from something brought into the tank with the new fish and the other fishes are eating their bodies.

Please take some pictures of the fish in the tank and tell us exactly what you bought and when it was introduced.

Look for any white spots, dots patches on the fish and see if any of them are rubbing on objects in the tank.

Check your water quality for ammonia, nitrite, nitrate & pH.

How often do you do water changes and gravel cleans and how much water do you change?

When did you last clean the filter and what type of filter is it?

 

[Yarkii]

how big is your tank?

200L

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[Yarkii]

Yes, what is the tank dimensions?

To answer your question, the Bristlenose will not kill cories that are healthy. They will feed on any dead fish, most fish will, so that is likely what you are seeing.

The clown loach might kill the cories, but from the little you have told us so far I would be more likely to suspect some pathogen was introduced with the new fish. Please give us more detailed information on this tank, the fish, when added, etc.

Hi Byron!

It's a 200L tank. At the moment I have four livebearers, seven young bristlenose catfish, three clown loaches, and it looks like only two remaining corydoras catfish. Since the new fish were introduced, it's only the corys that have suddenly been dying, including the juliis that I've had for about a year as well as the new peppers.

I have, however, been concerned that something beyond my testing ability has been going on. I lost a lot of fish a few months ago after my husband grossly overfed my fish when I went away for a few days. Since then the filter quickly develops a much blacker bacteria than I've noticed in the past. The water parameters that I can check seem fine, so I suspect there might be something I can't measure going on. But this new thing with a quick succession of corydoras dying seems different, given that the five juliis were healthy for so long, and that it's only one fish type dying.

Jacqui

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[Yarkii]

your fish are dying from something brought into the tank with the new fish and the other fishes are eating their bodies.

Please take some pictures of the fish in the tank and tell us exactly what you bought and when it was introduced.

Look for any white spots, dots patches on the fish and see if any of them are rubbing on objects in the tank.

Check your water quality for ammonia, nitrite, nitrate & pH.

How often do you do water changes and gravel cleans and how much water do you change?

When did you last clean the filter and what type of filter is it?

Thanks Colin.

I'll take photos tomorrow when the lights are on again.

The new fish (which admittedly I bought all at the same time) were 5 peppered cory catfish, 2 blond bristlenose and 2 clown loaches.

The existing fish prior were 5 julii cory catfish, 5 black bristlenose, 1 clown loach, 1 swortail, 1 balloon molly, and two young guppies.

Ammonia, nitrite & nitrate always test fine, although I'd like lower nitrate. I'll take new measures tomorrow & post them. The pH is always consistent.

Lately I've only done fortnightly water changes. I change between 70 & 100L of water at each change. I vacuum the gunk from the sand when I do water changes.

There hasn't been any flashing at all, but I have noticed lighter coloured patches on my swortail lately.

Jacqui

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[Yarkii]

Thanks Colin.

I'll take photos tomorrow when the lights are on again.

The new fish (which admittedly I bought all at the same time) were 5 peppered cory catfish, 2 blond bristlenose and 2 clown loaches.

The existing fish prior were 5 julii cory catfish, 5 black bristlenose, 1 clown loach, 1 swortail, 1 balloon molly, and two young guppies.

Ammonia, nitrite & nitrate always test fine, although I'd like lower nitrate. I'll take new measures tomorrow & post them. The pH is always consistent.

Lately I've only done fortnightly water changes. I change between 70 & 100L of water at each change. I vacuum the gunk from the sand when I do water changes.

There hasn't been any flashing at all, but I have noticed lighter coloured patches on my swortail lately.

Jacqui

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Also,

The filter & pump are in a sump under the tank. The water collects via an overflow filter chamber, drips then rises through three types of filter medium, then gets sucked up through a pump and back into the tank.

I clean the first filter media (white spongy filter) at every water change (in removed tank water) and since it's been noticeably unusually black lately, I've been replacing that filter media frequently (keeping some of it but replacing some of it - but last time I replaced it all as it was so thoroughly black).

I've never cleaned the other two filter medium, other than vacuuming up any loose gunk around/on them.

Thanks Colin.

Jacqui

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[Byron]

When you say tests (ammonia, nitrite, nitrate) are fine, please give us the numbers. "Fine" can mean very different things. This increased organics (the dark brown/black) in the filter is often associated with higher nitrates, and overfeeding cause them obviously, as would too many fish for the biological system to handle. We need to know the test numbers for these three. Also, do you have any of these in your source water? Test that on its own, nitrate is especially important here.

Your water changes are not sufficient. Once every week, on he same day, is minimal; and I wold change 50-60% of the tank volume at each. And vacuum the substrate, and rinse the filter if it is getting dirty (as you described).

You are going to need a much larger tank, six feet (minimum, 8 would be better) in length, for the clown loaches. This fish should attain around 12 inches, needs a group of five from early on to establish the hierarchy, and needs lots more space. Unless a much larger tank is in the works as a definite, I would return the clown loaches.

 

[Colin_T]

If the filter media is black (not dark brown) then that is anaerobic bacteria living in it. If it is dark brown then it is just rotting waste and should wash out clean. If the filter mat is still black after hosing it off, then there could be something dead in the drain pipe that is causing the blackening.
With trickle filters The top layer is designed to trap the gunk and prevent it from getting into the second chamber with the other filter media. You can hose the top layer (white sheet) off and it won't affect the bacteria on the other filter media.

If you have any other sponges in the filter they should be washed in a bucket of tank water. If you have bio-balls or other sorts of beads/ blocks, etc, in the filter, then that does not need washing. And you should continue sucking any sediment out of the sump when you do water changes

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If you ever have to go away for a few days or a week or so, just feed the fish before you go and leave them unfed while you are away. Fish can go for weeks or even months without food because they don't eat to keep warm. They get their body temperature from the surrounding water. The food fish eat is used to swim around and grow. This means they don't need food as often as terrestrial animals.

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The fact you are losing peppered & julii cories would suggest the peppered brought something into the tank and it is killing the juliis.

I would wipe the inside of the tank down with a clean sponge, then do a 75% water change and complete gravel clean. Check the filter drain pipe and return pipes and clean them if you can. Clean the trickle filter as well and see how they go.

In the shop we had a recirculating system where rows of tanks were connected to a huge trickle filter and sump. Sometimes we would get fish dying in tanks and couldn't work out why. We did water changes, gravel cleans & treated but still lost fish. Eventually we would pull the pipes off and we usually found a dead rotten catfish that was lodged in the bend in the pipe. We remove it and do another water change and everything was fine after that.

If you have a dirty sponge in the filter that will also cause problems and can encourage diseases or unexplained deaths.