Dead Cory After Substrate Change

[flippajh]

Changed from gravel to sand at the weekend, only a little 65 litre tank, everything fine, love the new look of the tank, water stats have been fine, but yesterday tank looked a little cloudy and there was a funny floating film on the mopani wood, it looked like browny black cotton wool but thinner.

Then the cory's wouldn't eat, the Betta wolfed down his bloodworms tho! So did another water test and the nitrite was up to 0.25, ammonia 0, and Nitrates between 30 and 40 (tap is 20), so thought I'd do a 50% water change and skimmed all the film off the wood and had a vac of the yuck on the bottom. Gave the filter a rinse out in the removed water. It was pretty gunged up.

Came in today to find one of my albino cory's dead on the bottom and after testing the water, nitrites are looking slightly purpler than 0.25.

Does this happen regularly when a substrate change is made, is there a lot of good bacteria in the old substrate. I understand from other posts there is a bit in the substrate, but wasn't expecting a spike like this.

I suppose the answer is just keep doing biggish water changes?

Thanks

 

[markandhisfish]

unless you use an under gravel filter the bacteria in the substrate bed is minimal. you say you have a film . did you wash your sand?

 

[tom_os]

all my cories survived a substrate change

 

[Inchworm]

Hi flippajh

This should not have happened. What kind of sand did you use?

 

[shelaghfishface]

cories have an inbuilt "cyanide pill" that they will eat if they are stressed.. i read this in PFK - u maybe able to read this on the website,did u take the fish out when u changed the substrate.. think what we need here is some one who knows there stuff on cories.. although the theory wouldnt support the rise in nitrites, what about ur ammonia reading? maybe u murdered the filter bac in the change over process.. test again , dont do massive WC do about 20% this will bring it down and stress the fish less at the same time... then test again, then if u need to do another small WC a few hours later,and try to match the temp, and dont forget to declorinate

theres plenty of good advice readily availible so any more probs or Q`s dont hesitate to ask

shelagh xxx
ps. sorry for ur loss

the film i suspect is from the bloodworm, a sheet of kitchen towel placed gently on the surface of the water will remove this

 

[Inchworm]

shelaghfishface refereed to something that can happen but doesn't usually. Some species are more apt to do this than others. I've only run into this once myself (with an overnight shipment of rare corys) and heard one other story about it from a breeder at an aquarium society meeting.

But, by all means, do what you can to reduce the nitrite.

 

[flippajh]

The sand was silver sand from the lfs, I rinsed it about 5/6 times until the water coming off it was clean.

I emptied half the water into the poly box from the fish shop I kept from when I moved other fish around. Then put the fish in their, 4 albino's, 3 melanistius and my betta.

Emptied the rest of the tank and left the filter in this bucket.

Threw the old gravel and then gave the tank a good rinse.

Put the sand in, replanted it, then filled it back up with warm de-chlored water.

This probably took about 2 hours in total, so I suppose the filter wasn't getting fed during this time. Perhaps this may have affected the bacteria.

Made sure the temperature was about the same as the temp in the poly box, then popped the fish back in.

Tested the water the day after, all readings fine, 0, 0 and 20 for nitrates, this is the same as the tap reading.

I then noticed this film, but it was thicker than a film, it was all over the mopani wood, it was thick, I could scoop it out with my hands and it was a brown colour, almost like a really, really thick algae, so cleaned the wood up and thought I'd better do a water test, and noticed the nitrite spike, so tested everything else, definitely no ammonia, but the nitrates had gone up slightly but not much.

Pictures below

So did the water change and then today, poor little albino dead. Water stats 0 amm, over 0.25 not quite 0.5 nitrites and 30 ish nitrates.

Very confusing. Have done another water change this evening, so will keep doing, 10 litres at a time, it's only a 65 litre tank so hopefully, this will bring it back soon.

Am worried about the rest of the fish now. Everything has been great in there for the last 8 months.