Shrimp Tank With Green Stuff

[Tanuke]

I have had a brackish 5 gal. opae ula tank going since June. It has live sand and lava rocks (not live rocks), and a sponge filter going at a very low bubble. I was told by the Hawaiians I got the shrimp from that they don't like filtration since they normally live in ponds and lava tunnels/caves. The shrimp seem to be doing just fine but there's this greenish-yellow stuff (looks like slime) "growing" on all the sides, rocks and sand. Is this algae gone wild? Or is it really slime from some inbalance? The shrimp sometimes feed on it but there aren't enough shrimp to clear it away. Should I scrap it off as best I can? All winter I've only been feeding the shrimp a pinch (literally) of powered spirullina once a week so it can't be from overfeeding. Is there anything else I can do? The tank does sit on a bookcase in front of a window but it's got a background sheet on 3 sides, and the tank light is only a 15watt incandescent bulb. Advice and suggestions? I want to disturb the shrimp as little as possible since this is their breeding season.

[wrasser]

due you use tap water to refill the evaporated water?

[Tanuke]

I'm using distilled water since my tap water comes with a load of chloramines. I think it's probably algae--I tried scrapping it off and it kind of gently floated around in sheets until I could remove it from the tank. Too much light I suspect. Yes?

[wrasser]

its probably a combination of things, water inbalance and the amount of time you leave the lights on.