First turn off your filter and any powerheads that are circulating the water.
Wait until the water has stopped moving completely.
Then look at the surface of the water from below, with the light on, and see if there's appears to be an Oil "Slick" formed or if the bubbles start to pop.
If there is a slick or if you dont see anything still try this:
Twist up a paper towel and stick it in the water so it pierces the surface only an inch or two.
Pull it back out....Does it leave a spot that appears cleaner???
Does any of the water droplets from the paper towel that fall back into the tank make a clear spot???
Most of the time I found that a "Slick" will appear if the tank has been overfed, if any leftover food has not been removed after the fish have had their fill, or if I have not washed and dryed my arm before vacuaming.
I've found this to work in the past:
Turn off all filters and powerheads.
Wait until the water calms.
Place the siphon in the water slowly with the open end up.
Slowly stick it down in the water so that it skims off the top.
Only let the siphon tube get about 3/4 full.
Pull it out and dump that water...repeat until the Slick appears gone.
Replace water to normal levels.
Turn the Filters/Powerheads back on. _________  |