Stubborn surface biofilm?

[lilsd]

I recently added a few new fish to my 10gal tank, and for the last week there’s been a lot of biofilm on the surface. I’ve been removing it daily with paper towels, but it keeps coming back. The tank has been cycled and doing well for 6+ months now, but I remember having this same issue for a few weeks early on. It eventually went away on its own, and I don’t think it’s harmful at all. Plants and fish/shrimp are healthy and the water parameters are stable. But it’s an eyesore and I’m curious if anyone knows what causes this? Is it related to adding the new fish?

 

[MattW]

Water stagnation is my guess. I'm guessing that tube/barrier across your filter? is blocking water flow on the surface. You could run a mini air-driven filter or air stone to help break it up elsewhere in the tank.

 

[Jinx_]

Tale water out from the surface, so just take out the biofilm. Increase surface agitation, like a skimmer or a stronger filter, an air stone. Problem solved. Anyway over time it settles and goes away on its own.

 

[lilsd]

Ah, yep that does make sense. I put the tube there because I have floating plants that were getting ripped around by the filter/agitation…

 

[MattW]

Simple fix for floating plants and water agitation is a plant ring. Similar idea to what you have done but instead of isolating the water outflow you isolate the floating plants. Only a small area of the waters surface would become stagnant. I used to have a couple I made myself out of airline hose. They can be commonly found on Etsy and eBay