grey slime on filter

[Phoenixphire55]

I have a 10 gallon tank that houses a small school of feeder guppies, 3 crayfish and a fiddler crab. I had it about 1.5 months with the guppies in it, and then the crustaceans have been in it for the last month. They all molted within a week of each other, and another week after I did a 50% water change. From now on I'll be doing water changes a lot more often, just was waiting for them to get used to their home. Anyway, I noticed a greyish/ pinkish slime growing above the water line on the glass next to the filter, directly above where the bubbles from the bubble wand were coming to the surface. The slime extended onto the top of the filter and inside onto the permanent part of the filter. I continued out over the filter lip thing, and ran down into the water like a bunch of hair. I'm wondering what this is and if its dangerous to the crayfish / crab. I cleaned 90% of it off but I know it'll grow back. Yuck

 

[theotheragentm]

Your tank is most likely undersized for the crayfish. Plus they are territorial. Look into getting a bigger tank. Fiddler crabs need brackish water i thought. I'll let someone else confirm that.

As for your original question, I'm not sure where the film is coming from, but you can take a paper towel and blot the top of the water's surface to pick up leftover oils from foods and wastes. This should help a little bit.