Hi all so basically tonight I saw an add on gumtree advertised that was 4 fish for sale but seeing this add absolutely shocked me and I knew that I had to rescue these poor fish. So from the photo I could see 4 shubunkins, one of them was pretty big around 4” or so, cooped up in a tiny tank that looked around 15-20 litres big and the water was so brown that I could barely see the poor fish so they were clearly being neglected by uneducated owners. I have a 170 litre tank and even though I know that this tank is too small long term for 4 shubunkins and it should ideally be only housing 1/2 shubunkins, I will be upgrading them/ putting the bigger ones into my uncles pond in the summer but also let’s be honest I could not leave the poor things cooped up in a tiny filthy tank and suffering when I could keep them in a much bigger tank short term until they get bigger.

So any way I collected the fish and I could barely see them in the fish bag the water was that filthy but from what I could see the poor things looked really ill. So after getting home, I test the water that they are in and within seconds the ammonia shoots to dark green which is the highest colour on my test strips which is 8ppm and then it began to turn blue it was that off the scale. After nettitng them out I was able to get a proper look at them. Two of the fish seem perfectly fine and unaffected with no visual issues. But one of the fish has part of its top fin on its tail missing and its fins are all clamped and it has red streaks on its tail which I’m assuming is from the ammonia stress. The other is extremely lethargic, its fins are clamped and it’s lying down constantly and I can tell the poor thing is on its way out.

My plan is to move the two ill fish into a smaller isolation tank that I already have set up so that I can add some aquarium salt in there to help with the stress but also I am hoping it may help with their illness. My plan is also to add a heater in there at around 23 degrees as I’ve read online somewhere that this can help with illness. My question is though is that is this the right thing to do for them as I want to try and save them so bad as they deserve to at least have a chance in life after what they have been through but as I’ve never had to deal with ammonia stress before in coldwater fish I’m unsure if this is the correct way forward. Any advice would be so helpful!! Thanks in advance everyone :)

Well done for rescuing them from such horrific circumstances. Your immediate and longer-term plans to me sound fine.

The fish will be continuing to suffer the after-effects of their chronic exposure to ammonia and no doubt nitrite (each at high levels) and high nitrates. Just to forewarn you that they may not recuperate from this, and even from the sudden change to good water quality, but it's definitely worth trying your best as you are doing. If I were you, for the isolation tank, I would dose just a small amount of the aquarium salt to prevent any inadvertent additional shock to them. While it sounds as though there is finrot in one of the fish, I'd probably advise not dosing medication for now and see if the improved water quality alone (perhaps with a small dose of aquarium salt) in that tank might help. Hopefully improved water quality alone will help the healthier-seeming fish going into the 170-litre tank.

Whether you have existing fish in the 170 litre or not, you'll need to monitor ammonia, nitrite and nitrate in both it and in the isolation tank, as I expect that there will be some degree of cycling/mini-cycling occurring to the filters due to the added bioload. Monitoring water quality daily and frequent small water changes will be key to keep ammonia and nitrite at 0 and nitrates at no more than 20 above whatever your tap water level is. This ought to give the fish the optimum chance of pulling through.

A liquid-based test kit to monitor ammonia, nitrite and nitrates over the next month or so at least will be crucial. This is actually more important than buying a heater for the isolation tank (even although that may possibly be of some benefit).

Best of luck!

Thank you for your response, I test my ammonia, nitrites, nitrates etc every week anyway so I will undoubtably test the 170 litre and iso tank as I won’t be surprised if the ammonia spikes a little. I’ve transferred the two ill ones to the iso tank and I’ve found a spare heater I have already which I’m using now for them so hopefully that and the salt I’ve added should help. I don’t think it is finrot as the fin doesn’t have a white edge to it but I’m definitely going to keep a close eye on all of them so hopefully it wont be fin rot and fingers crossed they can all recover from this. It’s just a shame that the old owners didn’t care that much about these beautiful living things :(