filmy surface

[reybie]

I just noticed something filmy on the surface of my cycling tank. What could this be?

[Chrona]

It's dissolved organics leaving a film at the top. You can remove it by laying a sheet of black and white newspaper (not color) on the surface, letting it soak in, then removing it. The film prevents the exchanging of gasses at the surface, so for most tanks, it's a bad thing.

[reybie]

Thanks! I will do that first thing when I get home tonight. It's really noticeable when you're looking up at the light from below the tank.

Do you think this is from the used gravel?

[Chrona]

It's possible. I usually find I get more film when I overfeed though.

[xoolooxunny]

that newspaper sounds like a good idea. Another thing you could try is just pulling the return out of the water a little bit. It mixes the top of the water, and it has a chance to get filtered. worked for me, then i stopped overfeeding:jaws:

[reybie]

I read a post somewhere on the net about fitting a pvc pipe upside down sort of like a surface skimmer temporarily to suck the filmy stuff out and get it trapped in the filter. Too much work though. I'll try the newspaper trick first as soon as I get an old one.

[reybie]

I finally got rid of the slimy stuff! During the first few days of the cycling I only had the eheim canister filter doing all the work. The intake sits in the back left corner of the tank and not much surface agitation. After fiddling with it for a few days I thought of using one of my small HOBs to create some surface movement and it worked!

I put it in front of the tank temporarily so that the water output was dragging surface water down directly to the intake. A couple of hours and the top surface was clear of oil slick. I'm not sure if it will come back after I remove the HOB, we'll see.