Oily film on surface
I've recently added live plants to my well established tank (up for 2+ years now). The flora is minimal as I have a group of Geo's that would love to dig up any plants rooted in the substrate.
I recently made a few changes to the tank set up - one of which I suspect is causing the oily film that is now on the surface of the tank. (I know…bad idea to do make more than one change at a time to easier identify the root cause of problems - just like this one!)
2x Emperor 400 HOT filters
Penguin 1140 power head (300gph) w/ quick filter attached
The additions to the tank:
LARGE piece of driftwood (much too big to boil - so I just hosed it off)
small piece of driftwood w/Anubias nana attached
pastic mesh from a craft store (I attached java moss)
4x Anubias Nana
2x Java fern
LOTS of Java moss
5x 3" Geo's
10x 3" Congo Tetras
1x 4" Severum
3x 5" Pictus Cats
1x 2" Royal Pleco
1x 3" Common Pleco
1x 4" Khuli Loach
I've done 25% water change every day for 2+ weeks. Additionally I have skimmed the water surface with each water change - some times 2x a day.
The skimming would only temporarily relieve the problem. The oil slick would start coming back over night. I've tested the water and all appears normal. Ammonia = 0, Nitrites = 0, Nitrates = 10-20, PH = 7.5
I have considered setting up a protein skimmer - but really don't want one. The fish all appear to be thriving - but the oily surface and resulting foamy bubbles are most certainly hampering the oxygen exchange at the surface.
Does anyone have any insight on how I might better address this problem?