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Dear All,

I hail from the tropics and have a 6 foot tank with a sump tank system with an arowana and some silver dollars. I went away for a while over the new year holidays and came back to find that there was an out break of mosquito like insects. I don't understand how it happened but I am thinking that those aren't mosquitoes. Reasons :-
1. The larvae I found in the water were unlike the wrigglers you see on the web, their bodies were thin with large bulbous eyes and they "wriggled" very vigorously unlike how the wrigglers would. Their bodies were segmented with brown lines, according to my wife.

2. There were no trace of pupae when I tried to remove some of the water from the tank.

3. The adults did not seem to bite. One possibility is that those were male? I noted that they were smallish in size as compared to the conventional mosquito with feathery antenae and their posture had their bodies horizontal to the ground. They tend to fly in swarms.

Hope to get some ideas as to what they are, the larvae move too fast to be photographed so I can't provide much of photographic info. As an act of desperation we have been resorting to bug spray around the tank. We have a baby in the house you see.

Any advice on what you think the insects are is appreciated. What can we do? I intend to overhaul the tank this weekend with some crazy cleaning. Hopefully that will solve the problem.

Try Rosie Reds. Some use them to control mosquitos in ponds. If nothing else, the Arowana will enjoy them as a snack

Do they appear anything like midge flies, specifically Chironomids, which are known as non-biting midges? With my limited entomological knowledge that'd be my first guess.

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The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.

Hiya guys,

Thanks for the thoughts. I did some work on the net with my wife and it seems to draw that conclusion as well. Question is that this has never happened before in my years of fish keeping and how did the midge larvae get in there? My dad has been using blood worms to feed the fishes so could that have been the problem? I dunno about the rosies, think the arowana is the only one which is going to benefit.

Hmmm, if the bloodworms were live that could indeed be an issue. Larger arowana are not exactly insectivores, and silver dollars, though they may eat bloodworms, are primarily herbivorous. All in all, bloodworms are not exactly a food either of your fish species would likely feed upon, so IMO leftovers are likely if enough bloodworms are thrown in.

Also, of course, there is the chance a midge got into your house and laid eggs. They're pretty small, of course, so it's possible they could have entered in this way.

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The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.

Hiya Shini,

Actually, the arowana has been trained to take bloodworms, which are frozen. We give the silvers pellets. I don't think midges tend to be common where I am that's why I am baffled at their appearance. Is it possible that the larvae came in through the bloodworms? Maybe some way the eggs or the larvae are placed in cryostasis or something? It still does not explan the lack of pupae actually.