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I have a 10 gallon tank that had three tetras and an algae eater. A couple of weeks ago, I noticed the appearance of water fleas in the tank. They have since killed two of my tetras, and I cannot get rid of them by water changes and vacuuming. That is the only remedy I have seen recommended here.

Does anyone have any other suggestions?

I don't know about water fleas, but what type of Algae eater do you have?. If its a CAE just take it back to your LFS, as a 10 gal. tank is too small for him.


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I don't think water fleas will kill your fish...if im not mistaken water fleas are also called daphnia, which is actually a food source of fish.

What makes you think the water fleas killed your fish? Tank parameters would help to see if it was just bad tank water. I don't see a way water fleas could kill your fish unless they were actually a parasite.

Last edited by Tetra Fan at 14-Aug-2005 18:50

It could be rapidly changing water parameters in your tank. 10g tanks are difficult to maintain properly and things like amonia can change rapidly.

Water parameters would be a good start to solving the problem . It could be high ammonia that killed your fish. So thats why it is important to post water parameters.

like tetra, water fleas are fish food. or so i thought

firstly we need to know how long that tank has been running for. if the tank is well established and has been running for a while there might be a chance its these fleas.

what are the size of these fleas? are they attachted to the fish or just on the surface? are there any spot/wounds on the fishes scales?

i was also under the impression daphnia were water fleas, which are a known food source for fish. if the tank is new-ish its more likely amonia spikes are the problem. did u cycle the tank?

is it daphnia or something else? ... because if it's daphnia, it can't kill the fish. daphnia, only eats algae, or green water ... it can't even kill a small fry. i even buy daphnia for my molly fry.

The tank has been running for over a year and all parameters are at normal levels.

I looked up the water fleas here:

www.microscopy-uk.org.uk/mag/artjun99/wflea.html

As you can see, it reads that some species are voracious predators. I have seen them attacking the fish (especially the algae eater, who likes to hang out on the bottom of the tank) and I have seen some wounds on the fish. If it is not they who killed the tetras, then I am at a loss for what killed them. The last one seemed happy and appeared healthy, and then one day he's dead.

Well, I did some more research and had an aquarium professional look at my tank. He said I actually have parasitic copepods in my tank. He recommended one of two remedies:

1) Treat the water with something containing copper, such as Aquarisol or Freshwater CopperSafe. Copper is toxic to invertibrates (so this would not work for tanks with crabs, for example) but safe for fish in treatment doses.

2) Increase the temperature of the water to 86 degrees for 10 days and add salt (1 tablespoon per 5 gallons).

I am going to try #2 since my fish are out of the tank anyway.

Andy,

Sounds like a good idea, given that you have no fish in it anyway.

I just wonder, how did he identify the parasitic copepods? Under a microscope?

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

'Predatory' water fleas are voracious predators, true, but only dangerous to organisms smaller than themselves. So their prey will typically be of the order of 1-2 mm in length.

Which in turn means that even small fish such as Neons will probably eat the water fleas. As my Cardinals and other aquarium inmates do with gusto every time I drop in a helping of live Daphnia!

As for parasitic copepods, if you have a positive ID on these creatures, then remove any fish from the aquarium, and give the copepods a large dose of dissolved copper. That will see them off in very short order.

I'd be wary of latching onto invertebrate IDs in the case fo such small creatures, however, unless your companion is a trained professional and knows how to identify such creatures properly. With small aquatic invertbrates, there is a LOT of room for error for the untrained!


Panda Catfish fan and keeper/breeder since Christmas 2002

To answer questions, yes the copepods were identified by a professional via microscope.

I have had the water at 86F for a couple of days now, and added 2 TBSP salt per 5 gallons of water. I also added an air pump to get more oxygen into the water since the temp is higher. The copepods are all but gone. To be honest, I think they hate the increased water motion more than anything else - they can't really control where they are swimming.

While the copepods are small, my source told me they are dangerous because they feed on the fish's outer mucus layer. They especially like the area in and around the gills - which can quickly cause death if there are enough of them.