Hi TFK :) I'm new to fishkeeping and this forum was recommended to me.
I have a 75L (20G) tank that was set up with no fish in it for 5 months (short version - I was extremely busy and had no time to do anything with it beyond water changes)
I had an albino cory from my first tank, and two weeks ago I put him in. Last week, he seemed to be doing well, so I bought another albino and two bronze corys for him to school with. The new albino adores him and follows him around when he's not doing his own thing. Both of them are doing completely normal cory things - very active, very happy wandering around. On the other side, the two bronze corys don't look great. One is VERY inactive. He sits still most of the time, and when he does move, it's in short bursts and he looks like he's having trouble doing so.The other one is doing slightly better, but still seems so inactive in comparison to the two albinos.
They do seem to be eating - when I go to check the tank after feeding time all four of them are in the area I drop sinking pellets. I just wanted to find out what was wrong with them and if I could fix it. I did take photos - sorry, they were taken with my phone and are too big to post directly. This is the one that barely moves This is both of them. The one that barely moves is towards the front This is the whole setup
I've posted in another subforum about the state of the plants.
KH - 5
Ammonia - 0.25
I did a water change (1/3) after the measurements so that should be fine.
NO2 - 0
NO3 - 5ppm
Water agitation seems normal - there's no film on the surface. I have recently upgraded my chemical filter and half of the bacterial noodles are now the ones that aren't the plain cylinder (I was told to change those out gradually).
I was planning on eventually adding a school of danios and some dwarf gouramis, but I want to sort this out first. Thank you in advance for any feedback and advice :)