Insect on top of water

[bruhaha2]

Hi all,
I've got a strange problem that I've only seen in nature at lakes or in a pond. I've got these little tiny insect that seem to be floating on the water in my aquarium. I've got a 29 gallon tank with a good bit of live rock(50 lbs or so), 4 hermit crabs, and 2 yellow-tail damsels. The bugs move around very fast and no matter how many I scoop out with a net, they seem to be back either later that evening or the next day. Any clues as to what these insects are and how to get rid of them? They are not very big, about 1mm and move very fast and only come out in the evening around dusk. I think I've seen similar insects floating on ponds before. Help!
Thanks,
John

[rshimek]

Hi John,

<img src="/images/welcome.gif" width="500" height="62"><br><b><i><big><big>To Reef Central</b></i></big></big>

The most common insect on marine tanks is a small flightless gnat or midge called Pontomia; see here (http://entomology.unl.edu/marine_insects/pontomia.html) for more information. They are harmless, if somewhat annoying.

I have attached an image of one, highly magnified.

[rshimek]

Hi,

Not a biggie, it just delays the answer. I always start at the first unswered post so some times I go back several days.

[bruhaha2]

Hi! Thanks for the reply Ron. From the pictures I've seen, I'd say thats exactly what I've got. I found this link that seems to describe them perfectly:
http://www.unk.edu/acad/biology/hoback/marineinsects/pontomia.htm
Anyways, nice call. I figured out a way to get rid of the adults. I've taken a spray bottle with a little bit of soap in it and squirt at the surface when I see them. This causes the surface tension of the water to change and viola, no more skaters. Oh a friend of mine also suggested motor oil but I was just looking to get rid of the bugs, not my tank. :)

[rshimek]

Hi,

The soap will kill the bugs. It will also kill a lot of inverts in your tank.... This may not be the best solution.

[bruhaha2]

Ron,
Any other suggestions to be rid of the bugs? My wife is a little concerned with having insects in the tank.... :)
Thanks,
John

[rshimek]

Hi John,

They are flightless bugs. They are harmless, and will not go anywhere. If you have a fish that eats things near the top of the water it may take them. Otherwise you can collect or drown them by floating a piece of paper towel over them and then removing it.

Regarding soap... one of the commandments etched in stone at labs that work with delicate marine organisms is to never use any glassware that has ever been washed in soap. Never.....

It dissolves many of the membranes of delicate animals.

[Phisher]

Sorry about the high-jack but does the soap thing apply to plastics and rubbermaid type products as well? This is all news to me.

Joe

[rshimek]

Hi,

Only if they are washed in soaps. Soap is designed to make fatty molecules soluble and it leaves a residue that is hard to remove; it can become soluble and affect delicate organisms. Plastics sometimes have toxic plasticizers, but most of these are not "food safe."