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New Member
Jun 10, 2004
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sheffield/notts UK
posted a message a while back in the breeding forum, cos my dwarf gouramis laid eggs. well i put them in a seperate tank, and they hatched..had about 50 fry. now ive only got 5..though they look quite well and are fairly big.

i have just noticed lots of hydra. id seen some a few days ago on the plants..and just changed some water and found lots more on the glass near the heater. am i correct in assuming this is where a lot of my baby fish have ended up?? and how do i get rid of them..i dont want my last 5 to die! ive read about putting electricity through tht tank, and vinegar..just not sure what is the best method considering that there are fry in the tank

thanks a lot
It was most likely the hydra that cleaned up the fry. I wouldn't mess with electricity or vinegar with fry in the tank. How big are the survivors? Could you set up another tank and move them into it?
i night be able to move them into a small godlfish bowl while i cleaned out the tank....i dont have another tank to keep them in. i only got this one in a rush when they laid eggs..couldnt even afford that one (nearly finished as a student!)

the fish are perhaps only a cm long..maybe slightly more, but they seem a lot bigger than all the others that disappeared. they are strong enough now to swim away from the sponge filter thing (i hope! just put it back in). i dont know how much of a grip the hydra guys have, but they seem small so id imagine mine would be able to get away. thing is ive been feeding them on live daphnia, and i dont want to be just feeding the hydra!

how to kill hydra

This little creature, anywhere from a third to one inch in length, is illustrative of how the guppy hobby carries us into related bypaths. Hydra are often introduced into aquaria with pond water and have become the "number one" enemies of guppies. To call them animals may seem like stretching a point if we judge from their appearance. A whole chapter could be written about them-here only the high spots. The animal attaches itself with a sticky substance to the glass or an object in the water. It cannot swim but it can move by a looping movement. The free end of the body has a conical projection called a hypostome on which its mouth is located. At its base is a circlet of long tentacles, five to ten in number. The hydra pulls the fry to its mouth by means of the tentacles, after interesting devices called menatocystshave caught it. Some of the menatocysts contain long spines in long rows. The prey is pierced and paralyzed by the spines which inject poison. Other cells have thread tubes in them which can lash out and wind around any protuberances on the fry to hold it securely, aided by a glue-like substance which it secretes. In a daphnia culture hydra create havoc. Hydra, when at rest, contract into soft balls. After eating, too, they retract into irregular globular forms. Because they reproduce both by budding and by fertilized eggs, hydra breed very rapidly. They are difficult to eliminate from a tank by washing it or even drying because their eggs have a hard outer shell which resists both drying and washing. The contents of the shell come to life quickly once favorable conditions are established.
A heavy infestation of hydra can destroy or retard the growth of many fry both by killing them and by eating their food which starves them. Hydra are easily seen protruding from their attachments and swaying about.
Treatment: (1) Hydra cannot stand chlorine or heat. If you have city water, remove the fish, drain tank and fill with fresh water. Return guppies two or three days later to the tank. (2) Remove fish, raise water temperature to 105' for 24 hours. When the water has returned to normal, return the fish. (3) Use of ammonium nitrite or ammonium sulphate at the rate of 5 grains per gallon of water will destroy hydra. Dissolve crystals in small amount of water first, then pour this solution into the larger tank. In 3-5 days all hydra will be dead, the guppies remaining unharmed by the solution.
wow :blink: hydra, i've never seen one of thsoe things before..can you actually see them move? does anyone have a picture :D
thanks for that...i work in a lab and we have some ammonium sulphate...its in crystals about the size of sugar, or smaller..im assuming these are the grains...might pinch a bit and try it...as long as it wont hurt my remaining babies.


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