Pygmy backswimmer (neoplea striola)

I was wondering if anyone has ever used these in an aquarium for live food for small fish. I am asking because I did an experiment and put a 5 gallon shallow container of pondwater (fairly concentrated with small creatures) outside this summer to see what species would takeover (and therefore be easiest to culture). I just went through the culture last weekend and the results were pretty clear. Besides daphnia and copepods there were three clear winners. Scuds (not sure which species), bloodworms, and pygmy backswimmers (neoplea striola). There were a lot more pygmy backswimmers than either of the other two. I know they eat daphnia though they are only slightly bigger than the largest ones in my sample, and I'm fairly sure they must eat mosquito larvae (at a small size)as well because none were observed in the tanks all summer, and there were zero in the culture at the end, even though it was right next to my fairly productive mosquito larvae tanks.

These guys are actually quite fun to watch in a small container on their own right as they are always swimming someplace and the bubble they carry around with them looks like a little drop of mercury in the water. They seem to have some advantages for culture:

1) easy to culture (I'm guessing they may be co cultured with daphnia or outside so mosquito larvae can be deposited), the tank remained green throughout the summer so there must have been some kind of equilibrium between the backswimmers, the daphnia, and the algae.
2) sized about 1.5mm-2mm long by 1mm diameter
3) active swimmers and easily visible to fish

I put some in my tank with my het formosa and they seem slightly too big for the males to eat. The big females should be able to eat them I think, but there are still a few swimming around after a couple of weeks in there. (not as many as there were though) Since the females spend most of their time hiding I'm not sure if the survivors are in there because they are lucky, or if they have some kind of defense (or just taste bad). The males will pursue them almost every time one gets close but they are so round it doesn't look like they can eat them.

Are the pygmy backswimmers that have survived in your tank eating the Heterandria formosa fry?

I've never seen (or noticed?) Neoplea, but if their venom is anything like the larger Nototecta then fish might avoid them after getting stung trying to eat one. Do the adults fly like Notonecta?

I added some Neoplea, along with various micro- and mesocrustacea, to a tank with Banded Pygmy Sunfish (Elassoma zonatum) and a tank with Pirate Perch (Aphredoderus sayanus) and Black-spotted Topminnow (Fundulus notatus). They had very high survivorship in the Elassoma tank, though I couldn't say whether the Elassoma avoided them or were unable to capture them. They were eaten in the pirate perch/topminnow tank, though they seemed to last longer than the crustaceans. I don't think the fish discriminated against them, I think the bugs were just better able to avoid predation than the crustaceans.

Are the pygmy backswimmers that have survived in your tank eating the Heterandria formosa fry?

They are about 1/3 the size of the smallest fry, I've seen the fry chasing them but not the other way around. Might be possible with other fry that aren't live born. I have some shrimp in the tank too, and they might be able to take the smallest shrimplets.

they struggle with even daphnia though, when they get one it's a struggle for a few seconds.

Edited by asmith, 25 October 2011 - 03:39 PM.

I've never seen (or noticed?) Neoplea, but if their venom is anything like the larger Nototecta then fish might avoid them after getting stung trying to eat one. Do the adults fly like Notonecta?

As far as I can tell they can't really do anything outside the water. If you net them they will just lie there, I don't think they can even flip over.

Oh! I was just hunting for info on what non-fish to put in my pond to eat mosquito larvae while I let it recover from ich. Glad I found this!