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Surface scum


4 Mar 2012
St Helens / Merseyside
Hi guys. Not sure if this is the right section but hopefully someone can offer some help. I seem to suffer terribly with the worst surface scum I've seen.

The tank is 30l, dosing excel daily, lighting is an 18w pc. Filter is an internal fluval but this will be changing to a much bigger canister in a few days.

In the tank are 4 dwarf puffers who get fed a small amount twice a day, anubias, java moss, a plant I don't know the name of, vesicularia and azolla. Flow is from the filter and I don't think it is strong enough. I added a 350l power head with spay bar to blast the surface to see if it helped. It did a bit, but it would still gather in the corners.


Here it is... It's gross! Oh water change is 25% per week using prime. I also feed APF plant nutrition once a day.

Help!!! 😡
I used to get that quite a lot and it's not uncommon. Ehiem make a surface skimmer to connect to your intake pipe. ADA also make one. Some folks think the oil content of some fish food contributes to the problem.
its coming from somewhere.... Either decaying plant or animal matter surely?
Hi all

You will see this junk in most planted tanks that do not have surface agitation (or very little).
It comes from a variety of sources mentioned above but it also comes from the plants themselves (proteins etc.), even more so when you have failing plants, because we are growing these plants up to ten times faster than they grow in their natural environment.
I have two hi tech and one lo tech tank. I sometimes see it in the hi techs but never in the low tech. To get over it I have my spraybars agitate the surface which constantly breaks it up. If all your plants are in good health you will see a marked decrease in the appearance of this 'scum'.
I would up your water change to 50% + per week too. It all helps.
Hi all thanks for the responses. The DPs get fed a variety of frozen foods, but only an amount they can finish in one helping, the wood is Sumatran drift wood. Ceejay thank you for that, I will up the water changes. As said I had 350lph power head with a surface bar and it did help but you could see an oily like film trying to gather still. Hoping the new filter will be here soon. Interesting you say you don't get it in the low tech tank, the tank is fairly low tech. It's horrible tho - is it worth trying to get a surface skimmer do you think or is it better to try fix the issue rather than just mask it?
The higher the light I use the more I've noticed I suffer from this surface scum. In my low tech I don't have any as the plants grow so slowly and I didn't have it in my last slightly higher but still low tech.

A surface skimmer is just a mask IMO.
Is the light to bright do we think to be just dosing excel? The plants in there are all suitable for low tech I think. The reason I got the azolla, I was hoping it would help break it up (it doesn't, it just gets stuck in the scum) and ailso to defuse some light.
I reckon a surface skimmer can be a useful addition to any open top tank - the ADA ones look nice ... 😀 but if you really don't want one you can try mopping up the scum with kitchen roll till/if it subsides. Float a piece of roll on the surface for a few seconds then scoop it up carefully and bin it.
The ADA skimmer is a complete rip off IMO. You could spend a £180 on far more useful things for your tank than that. In my experience surface scum comes and can go just as quickly. Regular large water changes seem to help with it.
Hi all
spookyspike said:
Interesting you say you don't get it in the low tech tank, the tank is fairly low tech.
Fairly low tech yes, but you're still adding carbon, which puts in the next bracket up from low tech.

Morgan Freeman said:
The higher the light I use the more I've noticed I suffer from this surface scum.
Thanks Morgan Freeman, this is exactly my point. The higher the lighting, the faster the plants grow so they produce more waste 😀
With higher light comes all the usual problems of more demand for everything like CO2 and ferts, plus their distribution. Get one of these three things wrong and your plants will suffer and your surface scum will increase for sure. 🙁
I have floating plants so can't scoop it out. You are right the ADA skimmer is a rip off. I think some large water changes are in order.
Is there anything else I should be doing I.e upping frets / excel etc? I'm always really cautious about over doing it with carbon dosing.
a healthy tank should not have surface scum. Unless it is leeching from wood and even new equipment can cause issues- but that should pass.
It is a fairly new set up (a couple of weeks), well the filter is out of an old tank which had been running for about 5 months, I used the filter and half the water out the old tank when I set this one up. But substrate and plant were all new. I used tesco molar clay value cat litter for substrate, it was rinsed really well but could it be something leaching out of that? The wood I'd soaked for a month before it went in the tank, it was also in my old tank.
I did have it in my current tank for the first few weeks after adding fish, once it's fully cycled/matured you may find it clears up on it's own.