Layer of Film, Scum

ReefSparky · #1 12/25/2007, 01:38 PM

I've had this layer of scum before. Last time the duration was about 6 days. It went away on its own. This time it's been over 10 days, and shows no signs of abatement. From what I've read, it's not uncommon, but it's unsightly. My protein skimmer is working as it usually does, with the main chamber being chock-full of bubbles.

My overflow boxes in the tank receive this film, but it doesn't make it into the UTubes; so it seems to stay on the surface.

Does anyone know how to rid a tank of this? Is there a quick certain method, or is it a "wait it out" sort of issue?

Happy Holidays, all!!!

tkeracer619 · #2 12/25/2007, 01:55 PM

Your overflow is over it's limits, the water should fall a bit before entering the u-tube to help skim the top layer.

I would get more overflow and add more surface agitation.

No idea what that is.

ReefSparky · #3 12/25/2007, 02:12 PM

Quote:

Originally posted by tkeracer619
Your overflow is over it's limits, the water should fall a bit before entering the u-tube to help skim the top layer.

How can that be remedied?

tkeracer619 · #4 12/25/2007, 02:26 PM

It really depends on where the problem is created.

If the drain isnt pulling water out fast enough that will cause it.

Some of those overflows are designed poorly, this could be the case. Do you have room for another u-tube? The overflow might just be too small for your tank.

It looks like the u-tube is maxed out or has an air bubble in it. If you can't add another u-tube then you will probably have to replace it with one that flows more water.

jeweldamsel · #5 12/25/2007, 03:35 PM

Or you can try to cut/lower the return pipe below the display tank water level. Such that the water will fall into the overflow box and the surface scum will go with it.

Ebmorri · #6 12/25/2007, 03:49 PM

Try raising the inside overflow box up. You want a waterfall effect falling into the box, the top teeth should not be level with the tank water level. Also make sure that you do not have an air bubble in the u-tube. Any way of getting a full pick of the overflow setup from the top and sides? Also what size return pump do you have?

tangtang81 · #7 12/25/2007, 03:57 PM

raising the overflow box wont do anything.
I agree with ebmorrin on making sure there are no air bubbles in the U-tube, also make sure the prefilter between utube and sump is clean. If it non of those problems try lifting your u-tube a little bit maybe 1/2 inch at a time and see what happens. If that also doesn't help.....check to see if one end of the u-tube is longer than the other and if yes.....turn the tube around.

Ebmorri · #8 12/25/2007, 04:02 PM

My thought on raising the inside over flow is that is if it is too low and the tube cannot move the water fast enough. In this case the water isn’t truly flowing it’s just a siphon water out of the tank.

tangtang81 · #9 12/25/2007, 04:18 PM

ahhh ic what you mean. However, it is a siphon either way you put it. the return pump is what dicates the speed of flow not the u-tube or overflowbox. so by raising it you simply raise the waterlevel. if you "open up" flow by cleaning prefilter/ adding another tube/ raising utube etc you decrease waterlevel and water will siphon better

jeweldamsel · #10 12/25/2007, 04:24 PM

By looking at the first picture, the water level is way above the teeth of the overflow box. It would help if you can post some pictures of the return pipes inside the overflow box.

sjm817 · #11 12/25/2007, 04:59 PM

Most HOB overflows cant handle a lot of flow (Lifereef being the exception). They cant actually handle the 600 GPH "rating". As others have already posted, to surface skim, the water must "fall" into the overflow. The water level inside the skimmer box must be below the bottom of the teeth. A too tall baffle or standpipe on the drain side can also cause this. If the drain piping is not restricted, cut back your return flow. Dial it back on the output side.

ReefSparky · #12 12/25/2007, 05:42 PM

Thanks for the input everyone. I'm using a standard overflow box with no baffle on the drain side. Unless I'm mistaken, lifting the utube will only decrease flow. Additionally, the utube must be longer on the drain side or the siphon won't work (at least in theory. As long as the water level in both tank side and drain sides are above the utube, the siphon will be maintained. Just as a simple garden-hose siphon only works when the drain end is lower than the tank water, such is the case with overflow boxes too. Unless there's some baffle to maintain water level on the drain side, the utube's longer side must be on the drain side.

I was also under the impression that 2 utubes won't help unless two drain lines are attached to the drain side box. As a poster above states, drain rate is dictated by return pump, but you can only hasten drain rate until the throughput of the drain pipes are maxed out, and I think I'm there.

I have two overflow boxes on this 55g tank. One goes to a 'fuge, and has 5/8" ID, the other, in the picture goes to the wet/dry/sump and has 1" ID tubing to the sump. The utubes are both 1" in each box.

To my experience the waterfall effect in the tank side box is what causes air bubbles in the utubes, consequently, my utubes never develop air bubbles.

I hope I don't sound contrary; but I've had this waterfall of which you guys speak, and always thought the recent lack of it was because I replaced my return pump with a hardier gph model, and the boxes fill more quickly as a result. I might just have to drill another hole in the bottom of the sump's box and add another outlet and a second utube.

Finally, to seal my fate and doom that much more--I have no filter floss or filter media in my overflow boxes. I don't like the variable they add to the equasion.

salty55 · #13 12/25/2007, 07:22 PM

it does look like you are exceeding the gph capabilities of the overflow box. If you have a smaller pump, try using it. or put a ball valve and a "tee" on the return so you can dump some excess flow back into the sump.

ReefSparky · #14 12/25/2007, 08:02 PM

Great replies, all. Thanks for taking the time.

Salty, it really hurts to take an action that's going to slow down tank turnover. Maybe I'll just have to break down and purchase a higher gph capable overflow box.

ACBlinky · #15 12/25/2007, 09:14 PM

Typically overflow GPH isn't really figured into tank turnover calculations - you want 3-5x tank volume moving through the sump/fuge, more isn't really necessary and can sometimes cause issues (such as bubbles, or possibly what you're experiencing). I'd use powerheads or a closed loop to provide more flow if it's needed, and try slowing the amount of water moving through the sump. If the overflow is better able to handle the amount of water going through it, your surface scum issue should pretty much clear up immediately

sjm817 · #16 12/26/2007, 12:56 AM

If you dont have/want the waterfall into the skimmer box, you will have the surface slick. No way around it. This is not unique to siphon overflows. Internal overflows are the same. If the level outside and inside the skimmer box are the same, it will not surface skim and you will have a slick.

I've been involved in several threads just like this one. The result is always the same. Fix the skimmer box level issue and the scum will clear in a matter of minutes. I learned this by having the same issue on my own system.

ReefSparky · #17 12/26/2007, 02:37 AM

Thanks, sjm. Thanks everyone too!

m2434 · #18 12/26/2007, 09:25 AM

Quote:

Originally posted by tkeracer619
Your overflow is over it's limits, the water should fall a bit before entering the u-tube to help skim the top layer.

I would get more overflow and add more surface agitation.

No idea what that is.

The skum just means the surface is stagnant.
If you don't want more flow through your sump, then just add a powerhead and point the powerhead up at it.. it will disapear withing minutes.

sjm817 · #19 12/26/2007, 12:37 PM

IME unless you are talking huge surface movement, the scum will just get pushed around. The purpose of an overflow with a surface skimmer is to skim off the contaminants that float to surface and send them down to the sump for filtering. Mixing them back into the water column does not accomplish that.

m2434 · #20 12/26/2007, 01:44 PM

It is a build up of proteins, they need to be in the water to be removed by the skimmer. I agree that increasing flow through the overflow is better, but IME a powerhead will work just as well. On my 75, I had that problem, and put a 200gph powerhead in, and pointed it up. At first the scum broke up and floated around, but then started getting pulled down. I think the surface tension of the big chunk had more power to fight the pull of the overflow. Once you break the surface tension, there is not as much strength and the overflow works better. I could literally could see the, now little chucks of surface scum, go through the overflow followed by the skimmer going CRAZY!

sjm817 · #21 12/26/2007, 03:00 PM

If the overflow is doing it job as designed and surface skimming, there is no build up of protiens on the surface. Its a very easy fix. If the level in and out of the weir are equal, the scum sits on the surface and the water just slides underneath it. I tried the powerhead route by adding an extra MJ1200 near the surface in addition to the Tunze Stream I already had. It just pushed it around. Fixing the overflow cleared it in ~ 3 min and it never came back.

ReefSparky · #22 12/30/2007, 02:08 AM

thanks for the responses everyone. I'll have to just eventually upgrade the overflow, or perhaps drill the tank.

Kannin · #23 12/30/2007, 02:18 AM

This happened to my tank and I tried raising my overflow... I tried everything and finally cleaning my overflow box did the trick. I put my hand in front of the returns and hardly anything was coming out. So, basically... not enough water was falling into my overflow box.

sjm817 · #24 12/30/2007, 08:48 AM

Quote:

Originally posted by ReefSparky
thanks for the responses everyone. I'll have to just eventually upgrade the overflow, or perhaps drill the tank.

Why dont you reduce the return flow and fix the problem? Put a ball valve on the output of the return and and dial it back. You dont want that slick on the surface.

ReefSparky · #25 12/31/2007, 11:10 PM

Quote:

Originally posted by sjm817
Why dont you reduce the return flow and fix the problem? Put a ball valve on the output of the return and and dial it back. You dont want that slick on the surface.

Well, I took your advice and "fixed" the issue temporarily. I placed a C clamp on the return line for about 5 min's and dialed it in until the return flow was restricted to the point where overflow box experienced a cascade. This was long enough for the scum to be eradicated.

It's just that if that were a permanent fix, turnover would have been reduced by over half.

Until I find a permanent solution, I'll restrict via C clamp to remove the film when necessary.

Thanks for the great responses, all!