Thanks everyone. I just started breeding angels, and keep getting white eggs. Yet, my ammonia, nitrite, nitrate, ph etc are perfect. I have 2 filters in my 55g. 1 has purigen and sponge. The other: sponge, nitra-zorb, and bio-bag. I'm switching the breeding tanks to sponge filters, but my main tank (the one I'm discussing here) I want to keep running with the hang-ons. I noticed the tubes were really dirty on the inside. It looks more like algae than bacteria. I also saw more brown spots on my fake plants than usual while doing my weekly water change, so I cleaned the tubes. I'll report what happens. I had never cleaned them before, to preserve bacteria, like others have said. Thanks for the feedback!