Oily film on surface

[Carissa]

I have this oily film on the surface of my tank. It's there all the time in varying degrees (sometimes there's no open area, sometimes there's a large open area with no oily film, usually it's somewhere in the middle). I've tried adding carbon to my sump and that seemed to help for a day or so, then it was back. I've tried sucking it off the top but it comes back. Is there anything else I can try aside from upgrading my skimmer (which is producing skimmate)? Do I need more carbon? I'm surprised my overflow box isn't sucking it off but I guess it's not getting filtered out. It's a 33g tank 20g sump and the amount of carbon I put it is about the size of two of my fists. Maybe I need to position it better to get better flow through it? I just have it stuck down in the baffle so some water goes through it but some will bypass it.

[Seige]

Is your overflow set up near water level so it's skimming off the surface water?

[metalhead]

You might try increasing circulation in the tank also... Either with a larger return pump or additional power heads. If your overflow is currently not removing the film though I would lean toward a larger return pump for more water flow.

[Carissa]

I have my return pump throttled back because my overflow box can't keep up if I run it full tilt (pump starts sucking air or overflowing the main tank). So a larger overflow box would probably be a better option than a new pump. Maybe another powerhead too, I only have one in the tank right now. I might be able to aim it so it agitates the surface better. If I had another overflow siphon tube, I wonder if I could increase flow down through the box? That seems to be the bottleneck in my system. Maybe I can make one.

[metalhead]

I have my return pump throttled back because my overflow box can't keep up if I run it full tilt (pump starts sucking air or overflowing the main tank). So a larger overflow box would probably be a better option than a new pump. Maybe another powerhead too, I only have one in the tank right now. I might be able to aim it so it agitates the surface better. If I had another overflow siphon tube, I wonder if I could increase flow down through the box? That seems to be the bottleneck in my system. Maybe I can make one.

Yes, another siphon tube should definitely work for you!

[metalhead]

Yes, another siphon tube should definitely work for you!

Or I should say an additional siphon tube

[Carissa]

Well I added some more out of tubing I had lying around. It did the trick as far as increasing flow. I turned my valve all the way up on my return pump. So I'll wait and see what happens now.

[metalhead]

Well I added some more out of tubing I had lying around. It did the trick as far as increasing flow. I turned my valve all the way up on my return pump. So I'll wait and see what happens now.

Great... Let us know what happens.

[Carissa]

Well there's not much change, it's maybe 10% better than it was. I have a new carton of carbon coming in so I'll try that when it gets here. I just added some sponge to the sump for particulate filtration, the water is not cloudy but has a lot of suspended particulates in it, maybe this will help the oily film too.

[metalhead]

Well there's not much change, it's maybe 10% better than it was. I have a new carton of carbon coming in so I'll try that when it gets here. I just added some sponge to the sump for particulate filtration, the water is not cloudy but has a lot of suspended particulates in it, maybe this will help the oily film too.

Hmmm... I was hoping that the increase in flow would move the surface water around enough to get everything back to the overflow but it sounds like you may need to add another power head after all but let's look at a couple of other things first.

I'm guessing at this point, based on your earlier comments, that you have one ore more dead zones at the surface, probably at the far ends or in the corners of your tank depending on where your overflow is located.

Questions... We should have addressed these first and I apologize but either way IMO more turnover flow is a good thing. Where is your pump return line located in the tank, how far below the surface and how is it directed? How big is your overflow and where is it located (I'm guessing middle) in the tank? How many siphon tubes are running and how big are they in diameter? How many power heads (I think you mentioned one before) are you running currently, how are they oriented/directed and what kind? How much surface agitation does there appear to be currently and is there any wave action at all? What and how much/often are you feeding? Also, since you added the additional siphon tube, is your pump running at full capacity, when is the last time you cleaned it and what is its rated gph?

There, that should get us started right! I don't think carbon is your problem at all. I do not run carbon regularly and have no problems with films of any kind. The sponge should be OK for particulate control, I use a filter sock myself and it works well. Just keep an eye on any filter feeders or other specialized feeders you may have and if they start to show signs of decline, remove it. Also, make sure you keep said sponge clean or you will eventually have nitrate problems. If I were you I would clean it every day or every other day minimum. Under no circumstances should you let it go more than a week w/o cleaning it.

[Carissa]

Ok here are some pics. The overflow box is on the left hand side, the Koralia 2 powerhead directly beneath aiming roughly towards the front center of the tank. The return pipe is on the right side and ends in a T fitting directing the water towards either side. You can see the sump there. The pump has never been cleaned (actually I was just thinking about that today), but the tank didn't have fish in it up until three weeks ago. It's been set up for about a total of 8 months with only snails for some months. I've had a hard time feeding my lawnmower blenny so I've had to put some pellets in there on a continual basis for the past few days, and there is more wastage than normal since the pellets get soft and break up after a while, but the film issue started before this. The oily film is only on the half of the tank opposite the overflow box, I wouldn't call it a dead spot, but if I put food in there it goes around in a circle on that side like a whirlpool. I could turn that T fitting to maybe direct the water in a different way. I'm kind of afraid that if I move the Koralia I will end up with a dead spot below the overflow. The white specks are pods. You can see the surface film in that last picture.

[Ninong]

An oily film on the surface of the water is caused by one or both of two things:

• The corner overflow is not drawing from the water's surface.
• There is inadequate surface water turbulence.

Make sure that the 'teeth' in the overflow weir are clear and make sure that you have good surface agitation.

P.S. -- I forgot to ask but I assumed that you are running a protein skimmer??? The protein skimmer removes these organics but only if it gets them. Surface turbulence is important because that's the air-water contact.

[Ninong]

Looks like you have everything at the bottom of the tank: the return outlet and the powerhead. One of those needs to be much higher up in the tank -- like just a few inches beneath the surface.

Either that or buy another powerhead and place it at the right side of the tank about 3" beneath the surface.

[Carissa]

Looks like you have everything at the bottom of the tank: the return outlet and the powerhead. One of those needs to be much higher up in the tank -- like just a few inches beneath the surface.

Either that or buy another powerhead and place it at the right side of the tank about 3" beneath the surface.

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I just moved the powerhead to the other end of the tank and aimed it higher. I think it might help because now there is a ripple across the whole surface and it is pushing the surface water towards the overflow. Hard to tell yet. I do have a small skimmer in the sump which does pull out stuff regularly.

[metalhead]

Looks like you have everything at the bottom of the tank: the return outlet and the powerhead. One of those needs to be much higher up in the tank -- like just a few inches beneath the surface.

Either that or buy another powerhead and place it at the right side of the tank about 3" beneath the surface.

I agree with Ninong as usual... I would move both up closer to the surface and then add another power head if that's still not giving you sufficient agitation. If you have enough current at the top it should translate throughout the rest of the tank.

Also, the vortex you described is a sure sign of a "dead spot" or inadequate current.

Keep playing with what you have for now and try different things until you run out of options... Then if you're still not satisfied with the results try another power head, I doubt seriously that you'd need more than 2 for a tank that size.

Hope this helps... Let us know how it goes. Sounds like you're making good progress so far.

[metalhead]

Good looking tank BTW!

[Seige]

I agree. Nice tank.

[Carissa]

Thanks.

The film is mostly gone. I can see the slightest hint of a film if I look at the right angle but it's a lot better. I think I'm going to get a different end for my return pipe so I can angle that better too.

[metalhead]

Thanks.

The film is mostly gone. I can see the slightest hint of a film if I look at the right angle but it's a lot better. I think I'm going to get a different end for my return pipe so I can angle that better too.

Glad to hear it!

[Carissa]

Well the film is back. I've bumped up my mechanical filtration and will try carbon again once it comes in.