Biofilm....

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Andrewz00

Aquarium Advice FINatic
Joined
Apr 12, 2010
Messages
592
Location
Whitestone, Queens, NY
it looks like the gulf oil spill in my tank.... ok well maybe not THAT bad.. but i am getting this oily looking substance accumulating on the surface of my water....

i have read that its called Biofilm? ive read on here about increasing surface agitation to relieve this issue... however... a lot of info is quite contradicting.

i have a 90 gal planted tank with a eheim 2217... the return spray bar is aprox 2" below the water surface pointed directly across the tank (length). there is no air stones so no surface agitation.

now i have heard that you should NOT have surface agitation in a planted tank because the introduction of that quantity of bubbles would essentially bubble all the CO2 out of the water and the amount of O2 provided by the plants was sufficient for the fish.

i guess i really have 2 issues here...

#1 do i NEED surface agitation? if so, how should i go about that without disrupting the CO2 needed for the plants?

#2 how do i rid the issue of Biofilm?
 
do you have slate in your tank? I've found slate to put off an 'oil slick' on the surface for the first few weeks. If it is biofilm, there are tons of ways to get rid of it. Im not 100% sure about surface agitation in a planted tank, but I'm pretty sure I've seen several post that unless you're adding co2, the change wont be much at all. You can take a dry paper towel and drag it over the surface, that'll get rid of it. I have alot of surface agitation in all of my tanks (even my planted tank, no co2 of course), and the plants grow fine (low light, low tech). I guess thats not any real help though
 
i tried the paper towel trick thing last night and it just seemd to push it around... not to mention i would prob have to use half a roll of paper towel.. its a 90 gal. 6 sq feet of water surface
 
i had this problem a week or two ago, in a 55gal planted tank with pressurized CO2.. and was also worried about dissipating the gas from the water. i moved my power head towards the top, which helped some... but i've since hooked up two of the smallest air stones, one in each of the back corners. my lights and CO2 are on a similar timer schedule (CO2 comes on an hour before the lights) so they are on in the morning, off mid day, back on in the evening, and finally off over night. i have my air stones on the opposite timer schedule of my lights/CO2, and i really only run into trouble with losing CO2 during the overnight period (because it's longer). my drop checker tells me that the morning CO2 level is sufficient again within an hour or two on being switched on. if you don't have them yet, i would suggest a drop checker, small air stones, and a power strip with timer settings. sooooooo much better than dealing with the biofilm.
 
Unless you are injecting CO2, surface agitation will only add CO2 to the tank, not subtract it.

Surface agitation tend to equilibrate the CO2 level with room air. If you are adding extra CO2, then sure, that would drop the CO2. But if you are not, then agitation is going to replenish the CO2 your plants used, and is actually a good thing.

However, breaking up the biofilm won't get rid of it. You will need to remove it somehow. Easiest way is to set up your filter so it will skim the water off the top. Or you can try the paper towel trick.

DIY surface skimmer for canister filter:
A DIY Surface Extractor
<Or you can buy a pre-made one.>
 
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