Hydra in fry tank

[S.T.]

Hi all,

I have a fry tank with about 30 fry in various sizes that has hydra all through it. I've actually been away for a fortnight and just come back to this disturbing sight...

The smallest fry are about 1cm. I don't know if they're big enough to not be effected by the Hydra. I want to do something about it, but removing the fry isn't an option as it's a heavily... heavily planted mossy tank. Odd I know but it always seems to get the fry growing fast.

Any one got pointers or ideas?

 

[dw1305]

Hi all,

I want to do something about it, but removing the fry isn't an option as it's a heavily... heavily planted mossy tank. Odd I know but it always seems to get the fry growing fast.

No, not odd at all. A lot of us specifically use complex, mossy tanks for raising our fry as the biofilm in the moss tangles creates a lot of extra live fry food. I use it as a technique for Apistogrammas, but even more so for smaller fry like Rams, Trichopsis pumila or Rainbow fish.

I think to chemically remove the Hydra you need to use a treatment containing "flubendazole", it is an anti-helminthic but also kills Hydra, Planarian and Snails. I'd only use this as a last resort.

My preferred option would be to let this lot of fry mature in the tank (I don't think that they will now be bothered by the Hydra) and then once they are removed leave the tank empty of fish, carry on water changes and make sure that any Daphnia etc are netted out. Your Hydra should rapidly reduce in number if they aren't fed, just carry on siphoning out any you see.

Some fish will also eat them, Trichopsis pumila and Poecilia caucana come to mind, but there are probably others. I'm pretty sure one of the Tetra sp. I've owned ate Planarians, but I can't think which one.

cheers Darrel

 

[Microman]

I use a 6volt battery with copper wires attached to both positive and negative terminals.
Place positive wire in tank at one end, negative at the other end and leave for 30mins-1hour, longer may be required as it is dependent upon tank size.
You will rapidly see the hydra die off....
The beauty of this is it completely clears the tank of hydra and the young fish are not affected whatsoever. I have never had fry suffer from this treatment and have used it on tanks containing very small fry of less than 5mmTL.
Mark....

 

[dw1305]

Hi all,
Mark that's interesting, I've read about the copper electrode and battery method, but I never met any-one who has actually used it. Details here.

<http://www.thekrib.com/Fish/hydra.html>

It will also kill shrimps, so don't use it if you keep them.

cheers Darrel

 

[Bilbo]

I was told about this as a kid to kill snails.
Never tried it on hydra. I did use fluketabs on them and that did the trick.

 

[Microman]

Hi Darrel,
I must admit that i feed BBS quite heavily in my Apisto grow out tanks and as a result i have hydra quite frequently.
This method of eradication has been very successful for me with Apistogramma, Microgeophagus sp.,Biotoecus and Dicrossus sp. as the young have not been affected at all.
You are correct that it is not good for tanks where invertebrates, snails etc are present.
Mark...

 

[dw1305]

Hi all,
I've had Hydra once or twice in the Daphnia tank, my suspicion is that they only become visible when there is lots of potential prey in the water column.

I've had a think about why the dissolved copper doesn't effect very sensitive fry like Dicrossus, Biotecus etc. and I think there are 2 major reasons.

1. The fish naturally inhabit acidic, very base poor water and under these conditions any Cu+, Al3+, Fe2+ ions present in the environment will be available. I definitely wouldn't try the copper electrode treatment with animals from highly buffered waters (Lake Tanganyika cichlids for example)

2. The humic acids and DOC in the black water (or peat filtered tanks) will naturally chelate the Cu+ ions and remove them from the water column.

I think you could potentially use the copper electrode method and subsequently chelate the Cu+ ions from the tank by using Na EDTA as a chelator rather than waiting for the DOC to perform that role (FeEDTA wouldn't work as Fe ions are more strongly bound than Cu ions).

cheers Darrel