These days I found some grease-like thin cloudy layer on water surface in my new 29g tank. I never feed any meat, only vege and flakes and Reptomin. What are these and where come from? Is there anyway to prevent this from happening? Although it's not tons of work to remove by taking out some water, but quite anoying still. Thanks a lot!
(The tank is 30x12x18, with water filled about 3/4-4/5 African root lava rock some water plants sands. 1 3-inch RES and 3 tetra (1 inch))


