Thank you for all the information.
Unfortunately I have not been able to quarantine the sick fish. If you remember, I had a sick platy with a bent spine (who was the only obviously ill/lathargic fish) which I did quarantine in a 20L tank or so. However; I could tell she was not happy in the tank as she was spending even more time sat on the bottom, so I just returned her to the tank. Since I last spoke to you a few months ago, I think I've had 1 pygmy cory death/disappearance.
How is the platy doing now?
It's really strange because I've always had high nitrates, and practically no nitrites or ammonia (I presume this is down to the water change though). When doing the water change, I did the regular maintenance of the filter sponges i.e. squeezing them slightly in tank water and just generally getting rid of the bits on them. My filter is a Tetratec IN1000 (150-200L), and I have a 125L (33 US gallons) tank. My stocking is shown in my signature. I don't think I've used any medication apart from the Finrot one being used at the moment.
Ok, I'll feed them more often but less, and increase my water changes. I feed the cory's (I have a plec aswell) a few algae wafers every few days.
2 Glowlight Danios
2 Pygmy Corys
1 Mollie
2 Swordtails
16 Harlequin Tetras
Penguin Tetras
1 Platy
1 Guppy
2 Neon Tetras
2 Cardinal Tetras
1 Plec
2 Panda Corys
Hmm your stocking has a lot of issues in terms of the numbers of fish within the individual species.
Generally speaking, for pretty much all types of shoaling fish it is recommend that you have at least 5-6individuals within a certain type. So while you have a lot of Harlequin Tetras, the danios, penguin tetras, neon tetras & cardinal tetras are well below what their species numbers should be. Corys, platys, guppys & mollies should be in groups at least 3-4 strong (with the livebearers this depends on their gender ratios though).
If you had every fish in the right minimum numbers you would have;
5-6 Glowlight Danios
5-6 Penguin tetras
5-6 Neon tetras
5-6 Cardinal tetras
and the 16 Harlequin tetras. You would also have
3-4 platys
3-4 guppys
3-4 mollies
3-4 pygmy corys
3-4 panda corys
Plus a pleco (depending on its type, it could outgrow a 33gal).
But this would obviously seriously overstock a 33gal tank. But keeping fish (particularly shoaling fish) in numbers too low can stress them out. Treating diseases quicky & successfully of any sort is all about reducing the stress levels of the fish. Though not all your fish are healthy right now, i would personally advise sorting out the stocking when you have the finrot cured as it will be beneficial to all the fish. I would personally change the stocking to something along these lines;
10 Harlequin tetras
5 Neon tetra or Cardianl tetras
5 Glowlight Danios or Penguin tetras
3-4 Guppys or Platys
3-4 Panda Corys
3-4 Pygmy Corys
1 Pleco
* Concerning the livebearers you could have either 3females or 1male 2-3females or 5males. The Mollies are the largest growing & most active growing of all the fish, so i would personally have either the platys or guppys in an all-female or small mixed gender group. The guppys would have the least bioload strain on the tank.
Or something like this
. Whether you sort out the stocking issues now or later, it will benefit the fish a lot. Adding new fish though may risk introducing new diseases or parasites to the tank, so it might be better to do when you have a good quarentine tank set up running.
Well I did check the filter and I couldn't see a dead fish amongst the sponge (although I didn't see it in the gravel either...), and I do have quite a few plants in my tank, but I would have noticed the dead fish in the plant when I removed them while doing the substrate change I think.
If it was only a little pygmy cory then small fish like this can take as little as 24hrs to almost completely decompose, leaving nothing but tiny scull & spine behind.
And unfortunately I realise now that the bagging of the fish etc. could well have stressed the fish out and subsequently caused the finrot to develop; however, I'm not sure if I may have seen early signs of the finrot (whitish tips to their some of the their fins) before the water change; although I am not 100% sure. However, the high pH of 7.9 is normal for me (my tap water is normally around 7.8ish). When putting the plants back in the water change, I also put 2 pieces of bogwood in which had been out for 1 month or so (as I was seeing if this brought the high nitrate levels down while they were out of the water).
The net I used may be a bit rough- I have a finer net which I will use in future.
How will I reduce the nitrites/ammonia as I have never had high levels like this before?! Is there anything else I can add to the water to help the fish or replace their slime coats etc.?
Thank you for all the advice!
For the Finrot & slime coat repair there is a dechlorinator called Stress Coat by API ( http
/www.aquariumpharm.com/Products/Product.aspx?ProductID=43 ) which helps heal the fishes slime coats while also dechlorinating your water, its great stuff
. For the ammonia/nitrite problems just do daily water changes around 15% large to lower them (if they get any worse at any point doing a 30% water change)
.