This morning I woke up to find one of my cory's was dead, It had been out and about earlier in the week but did not come out to feed yesterday. It is part of a group of four corydoras trilineatus I have had for about three of four weeks now. They are in my 100 litre tank with twelve neons.

The dead cory was bent to one side and was missing its barbels/whiskers around its mouth.

I decided to carry out a waterchange his morning, probably about thirty percent and added some liquid ferts and a slight overdose of flourish excell

Now about two hours later another corydoras has started swimming around erratically, it is up the top of the tank and spinning trying with no success to swim downwards. it seems to have lost its ability to sink.

At first I thought it may have been the excess flourish excell because the other corys were lethargic and one was sitting up on a piece of driftwood not near the top of the tank. The neons are fine at the moment.

I have since done another waterchange and added a half dose of meth blue to the tank to help the flailing cory. My guess is that it has a swim bladder infection/injury of some kind. I have the injured cory in a floating plastic container and it is lying on its side trying to get upright every so often

The only other odd thing about the tank is that it smells a bit like cyano bacteria algae. I found a small amount of this out of sight among some plants when doing the intial waterchange.

Does anyone have any thoughts on what may be causing this?

If you think there is anything else I could do to help the fish recover?

All help would be appreciated

Thanks

Hi Fishkeepa. Sorry to answer your questions with more but........

How long has the tank been set up for? What is your water change regime? Can you test for ammonia and nitrite?

The tank has been going about five or six weeks now. The neons were to used to cycle the tank for about two weeks before cory's were added

I currently do not have a test kit, the water changes have been weekly when I am busy or half weekly if I can fit it in.

The biological filter may still be immature and the new fish will have increased the load on it. The bacteria population will take time to increase to accept that extra load. The water changes are the right thing to do....every second or third day if you can, more if necessary. I'd also stop dosing the tank with the ferts and Flourish for a while. Perhaps stop with the Meth Blue too. I think it treats external problems and won't help with anything internal.

Sometimes a LFS will test a sample of your water for you. It would help alot to know if the tank is fully cycled or not. A test kit is a handy thing to have because you can tell when an immature tank needs a WC and where it is in the cycle.

I recall seeing a post a while ago about someones corys dying after they had dosed with Flourish. I've searched for the topic but can't find it right now.

Whats your substrate like?

The substrate is sand, which I have collected from the local beach, it is pretty fine. I have kept corydoras before and have not had problems with their barbels on it

The smell from the tank is now gone, so maybe it was a spike in something olike nirite or nitrate or perhaps even distrubing some anerobic bacteria in the sand

The corydoras are active and feeding again

I will get a test kit once i get paid methinks

were there scars on the fish? almost like burn marks? patches where the slime coat has come off?

No I examined the fish and they looked fairly normal just clouded in the body and eyes. I haved one a quick scan on the other fish and they look fine, I am suprised that what ever it was has only affected the cories and not the neons.

clouded eyes? could be the flourish. particularly susceptible to fish that lack scales. take out the fish that are affected and put them in an established tank that has different water if you can.