I've checked the water today. Ammonia 0, Nitrite 0, Nitrates a little under 20 - which is higher than I like it. But that can come from the big and messy shrimp meal yesterday. PH: 8.0. I haven't checked GH and KH, but they never change here, and they always stay at GH: 3-4, KH: 2. All test are done with those liquid tests (pretty new ones too, and the very best I know of), except for PH which is done with a PH-pen (should have been calibrated again, but it never shows much wrong when it needs calibrating).
Tank size is 22 G, and Hufflepuff is the only one in there. Hufflepuff is a fully grown m. cochinchinensis or a not fully grown turgidus, I'm not sure. I've always felt that the tank is a little bit too small for him, but he has loved living in there. I have a bigger tank I could transfer him to, but I feel he would be miserabale there, as it's in my bedroom, and he wouldn't get so much action and attention there as he gets where he is now. So far, I'm absolutely sure that he has been happy with his life in that tank - that is until now. There has been some minor changes there, but he is not the kind of puffer who goes sulking because of that. The changes was two plants dying, being removed and new ones planted at the same places. I also washed the cover glass, so the light became brighter. But if that is what's bothering him, I can't see why he has moved closer to the light.
I feed him every other day, shrimps, snails (as treats), mussles, squid, bloodworms and my own home made discus food (not very often - but it's to make sure he gets some green stuff and vitamines in his food). Usually I do two 50 % WC a week, but lately it's been only once a week. I don't add anything to the water, as there's no clorine in the water here. But I do use some heated water. I know that can be a problem, but I've never had any trouble with it before (yes, I know you've heard that sentence before...
The tank has been running for about a year, so it definitely is properly cycled (which the water parameters also shows), and it's filtered with two internal filters. Both filters are small, but together they do a job that is well enough. As he has been alone in his tanks since last spring, there's no new addition to this tank, but I do share some of the same equipment with my other tanks, so it is possible to transfer illnesses that way.
I think I got all the right information there
BTW, Hufflepuff is my favorite puffer, so I am definitely worried about him. He has always been very interactive, and right now he has stopped being that - that's what bothers me so much. Something is wrong, and I don't know what it is!

