u/pearlight7

One of my kuhlis spends all its time in the leaves near the surface jammed against the glass - I have been able to account for all of them except one which has been missing for the last week, until I noticed it yesterday at the top of the tank. All my other kuhlis hang out on the floor together but this one is never with them. It occasionally has a wiggle to get in a different position but since I spotted it has always been in the leaves in this corner (apart from very briefly when I spooked it by accident). It's quite a vibrant colour still and hasn't paled or anything, but I'm just a bit worried about it isolating from the others - this is also the corner of my tank that has the lowest movement. I just am not really sure what could be wrong, as all my other fish/shrimp seem okay.

Ammonia = 0ppm

Nitrites = 0ppm

Nitrates - my test kit just ran out but I have one ordered, this is usually ~10-15 ppm whenever I check it though

Tank has been cycling a couple of weeks, I got it and the filter second hand but cleaned it all before use so don't think any established bacteria would have transferred over. I'm getting a lot of biofilm (?) growing on my wood and was hoping to get some shrimp in early to start cleanup, would they be okay or is it too early to add them? Nitrates were ~40ppm but I did a partial water change, are nitrites still too high? I ordered ammonia to test the cycle but it has taken a while to arrive still so I have just been ghost feeding. pH is ~7.5