Brown crud on top of water

[TNTCanada]

After about 3 or 4 days after I do a water change I always have this brown crud that starts to gather on the top of the water. I usually just move one of my power heads up to the top for a few days. After about a week I have no problems. Then I do another water change and start it all over again. Any ideas? :rolleyes:

[EmilyB]

What kind of skimmer and do you have good surface movement?

[TNTCanada]

Yes I do have a skimmer (CPR) it seems to work alright and I have decent water flow on the surface.

[EmilyB]

I just saw you had a 90g

Perhaps you need a larger skimmer? :confused:

[IslandReefer]

Hey Taz
Sounds like you are adding something or destabilizing the bios......
If you are using RO water check the differences in the parameters of old vs new for a clue...ie phos ppt.??
Also if you are into an experiment: Float new water in a jar etc in the tank (sump) and just a few drops of old water......a biological should grow if the new water is providing eg phos or silicate (ie poss. diatoms). And the reverse floater for old water supply of pre-crud....you get my drift..
Good luck

[TNTCanada]

Thanks for the input I'll give that a try
Cheers