It is definitely a chem question. Ammonia and Nitrite are 2 separate tests. Are you using a liquid test kit?
Also what is the brand of the additive you are using? I usually recommend Seachem's Prime but there are others out there as well. One thing of note is that the tank is a tad small for 2 SAPs. These guys (as if you haven't noticed) need lots of space and high flow. 55 liters is the minimum tank size for an individual.
I have a feeling it could have been either the chlorine in the water or an ammonia spike.
Kudos on the filter cleaning technique. Yes always use tank water to clean the internal parts of the filter. Especially the biomedia.
Other side questions:
How are you going about keeping their teeth trimmed or not over grown?
What is their staple diet?
Hi and thank you for replying to my post.
I realise now that the test kit I had was only for ammonia but I went out and got a nitrite test soon after I posted the previous message. Both are liquid dropper tests. The ammonia level was low and the nitrite level high. I've done a lot of reading while I waited to see if anybody would reply to me and come to understand that if the nitrite is now high and the ammonia low, my tank cycle could be on the mend and soon nitrate should return the balance and as there is nothing much else I can do. Is this correct? I have continued to do water changes two or three times daily, testing the water each time first and then afterwards.
I have been using Interpret's, "Bioactive Tapsafe" as an additive with my water changes and never had any problems before.
One of my puffers, the one which died before I posted, had no teeth problems. I only ever saw them start to grow once and they either fell out or he ground them down. The other one was trickier, and I had to trim his, although only once. He was a fussy eater.
I used to feed them all sorts; blood worm (live & frozen), cockles, muscles and baby snails, which I was breeding in another tank. The puffer with no teeth would crunch up the snails, whereas the fussy one would suck them out and discard the shells. He was clever. I sometimes soaked cuttlefish bone in blood worm and put that in the tank in the hope they would nibble it and help with the teeth. I don't' know if they ever did but like I said, I had no big problems.
Unfortunately my other puffer died early this morning. I did everything I could to save him with the bag floating being what I think kept him hanging on for the last few days. I guess it was too much. I'm absolutely gutted. My sunshine plec is still hanging on so I just hope I can get him through. I'm really going to miss my little puffers though - they were so entertaining.
Please could you explain what causes an ammonia spike?