Floating Green Sludge - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 5 Old 11-07-2012, 10:17 AM Thread Starter
Geomancer's Avatar
Floating Green Sludge

So for the past month or two I've been having a problem in my 125 gallon aquarium with floating green algae that I like to call sludge. I'm fairly possitive it is algae and not cyano.

Now, in my smaller tanks I've had that milky white-ish protein layer, but this is most certainly green.

I adjusted my canister filters spray bar to point upwards a bit so there is now surface movement on the left side of the tank. That area now looks far more clear. However, in the center and right side there are floating plants, and thus little to no surface movement.

I attempted to use a surface skimmer, but it gets clogged in a mater of minutes due to all the floating plants. I'm at a loss though on how to get surface movement.

I could use power heads, but I have fish who do not like currnts.

I could use a bubble stone, but I have plants and don't want to drive out CO2. I know that's a bit of an argument though on the extent of how much CO2 ges lost.

Any other options/ideas?

I thought maybe a nutrient imbalance or possibly too much light. For a few weeks I had forgotten to add my liquid fertalizer and I started to get a bit of a green water problem (not just on the surface). Starting up the fertalizer again has fixed that issue, but I still have the floating algae. There is also some hair algae on the driftwood, but haven't seen it affect the plants.

I'm wondering if I should try upping the dose to twice weekly, or if I should reduce the light duration (it's at about 10 hours now, dual T8 6500K, 24" depth). Nitrates are 5 ppm or less.
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post #2 of 5 Old 11-07-2012, 12:12 PM
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This is a protein bio-film likely due to high organics, but also may occur in part with no surface movement/disturbance and low CO2, according to the experts anyway. I have had it, and it was undoubtedly organics-related; the same tank also had issues with cyanobacteria which is organics-related too. It is always green is colour.

Another surface scum we sometimes see is whitish, and that is Eisenbacteria, an iron bacteria. Much different.

On the green protein scum, using paper towels to "lift" it off sometimes works, but I find it easier to use the gravel vacuum on the python water change apparatus, inverted so it slowly draws in the surface water. Starting at one end, just slowly move through the tank This doesn't work as well with a manual changer, as the reduced suction will keep stopping the flow. But with the python attached to the faucet it continues.

That gets rid of it, but then you have to keep it from re-forming. My experience has been that it will be around in this or that tank, sometimes for weeks and months, but suddenly it is gone. Right now, I have none in any of my 7 tanks.

Organics is the key. Remove all you can, perform an immediate major water change (up to 75% of the tank), rinse out the filter under the tap thoroughly, vacuum the open substrate during the water change. Same treatment as for cyano incidentally. Keep the light minimum, by which I mean sufficient for the plants but no longer. Maintain normal plant nutrient supplementation, whatever is needed for your setup to balance the light.

Increasing surface disturbance will help, but as you mention this has side effects that may actually "help" the scum by removing CO2.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #3 of 5 Old 11-07-2012, 12:38 PM
1077's Avatar
I too have expierienced this and surface movement with some floating plant's helped.
I also positioned my spray bar's(2), high on the back glass toward's the middle of the tank as opposed to one end or the other.
This arrangement makes it tough for the protein scum or sludge from collecting for it is forced down the front glass and back up the back glass continuously.
Also like the way tall plant's are pushed toward's the back glass and appear more upright, than leaning all one way, or the other.
Reducing light to eight hours would help in my view.
Just my two cent's.

The most important medication in your fish medicine cabinet is.. Clean water.
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post #4 of 5 Old 11-07-2012, 01:04 PM
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Pointing the spray bar at the surface will remove as much co2 as an air stone.

I vote manual removal and patience.

Originally Posted by Christople View Post
^^ genius

Soil Substrates Guide:
Part 1
--------- Part 2

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post #5 of 5 Old 11-07-2012, 01:19 PM
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Originally Posted by redchigh View Post
Pointing the spray bar at the surface will remove as much co2 as an air stone.

I vote manual removal and patience.

So long as your not breaking the surface, but rather creating a rippling effect,,there is no detriment to aiming spray bar's toward's the surface.
Been running mine this way for nearly a year now, and notice no negative affect on plant's.
Now,,positioning the spray bar's above the surface,,is another story.

The most important medication in your fish medicine cabinet is.. Clean water.
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