Bubble/Foam on water surface

[H]-[H]

There is a little foam accumulating on the water surface of my tank..
Is it bad for fish? Only on one side of the tank though..

 

[Dr Joe]

What I've found is there is something causing excessive surface tension. Oil from fish food, fish shedding slime coat, algae.
Need more info on the tank.

Chemistry, bio-load, food, filtration to start.

Dr Joe

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[tcarswell]

This is happening on my moms overstocked 20 gallon whenever i go there we end up doing a 75% water change. I swear she has like 13 mollies 2 platy's in a 20 gallon. Glad I talked her in to getting an Eheim 2213 finally (to complement her ac50). Once that thing gets well seeded she should be OK.