Hypoxia and Medicine

Why is my Molly hanging at the surface?

I have 3 mollies, 3 cory cats and 20-something molly fry in a temporary 48 litre tank (they're only going to be there for a week, don't worry). My male dalmation molly is hanging at the surface, with one of the fry, like he has hypoxia. I have an Interpet power filter with aeration built in. It is not working as well as it used to, but is still working fairly well (I think it needs a clean). Is this just because of the overcrowding? I can't see any signs of a gill disease. Do I need more aeration?

Public Comments

1. It sounds like hypoxia, either from poor aeration or ammonia poisoning. Definitely give the filter a good rinse with tank water, and carefully do a 30-50% water change. Clear out any gunk that might be clogging it, but don't replace the media, as the last thing you need right now is an ammonia spike (from removing the nitrifying bacteria). Also, lower the water level about 1/2 an inch, as this will increase aeration by causing the water to splash more.