In my QT tank (10 gal) my fish seem to be staying mainly at the water surface (not all, mostly the mollies, minnows seem to be fine under the rocks). From what I understand, this means low oxygen. I'm wondering how I can possibly fix this issue. Currently the tank has an HOB filter, a sponge filter I made using a sponge and airline tubing connected to an air pump, and a powerhead. I thought oxygen would be fine with all of this water movement and the bubbles caused by the sponge filter. Or am I wrong? Thanks for any help/suggestions!
Also, the tank had a 50% water change today (will have a 50% water change every day until fully cycled). The tank is pretty overstocked for it being uncycled but the guy I got the mollies from REALLY filled the bag up and gave me more than I thought. I do not have a filter cartridge in the hob but instead put a sponge in there and several pieces of scrubbing pads to aid in the bacteria build up for the cycle (plus gravel from main tank and water siphoned directly from main tank gravel in the hopes that that would add to the bacteria as I know it doesn't free-swim but lives in the gravel). I've lowered the temperature hoping that will help with oxygen.