Hydras Discovered In Tank Cycling For Shrimp. What To Do? SOLVED

Just checked the tank I'm cycling for the shrimp and spotted hydras growing on the glass plus some tiny worm like things. Obviously the hydra pose a threat to the shrimplets.

Is there any way I can get rid of them without resorting to chemicals?

All the methods I know are chemicals, which would take a while to clear from the tank before you could risk shrimps. But if salt would do the trick, that would be quite easy to remove by water changes.

Hydra will eat anything that moves and comes into the range of their tentacles. I do wonder where they come from. I recently took some thread algae out of a tank and put it under the microscope just out of interest. I was surprised to find large numbers of tiny vegetarian water mites, quite harmless to the fish but would make plenty of food for hydra. There are probably more things hiding away in our tanks than we think Realistically, I think they must all originate with plants. Many water invertebrates have resistant stages as their habitat is always likely to dry up and they need to survive for when the next flood arrives.

Thanks folks.

There's currently only plants in there and the shrimp cant go back in until the filter has cycled.

So it raises the questions which would be most toxic to the plants and easier to remove after ?Salt or copper?

Salt is recommended by quite a few sources. One I use is the "Fishlopedia". Although it's quite an old book (1999) I find its info very useful, frankly better than most internet sources. This may be because the main author is Dr Peter Burgess who is actually a fish health scientist and should know what he is talking about. This book is one of those that recommends 0.5% salt.
True there are many hydra relatives in the sea, in fact the vast majority of coelenterates are marine. But freshwater hydra would not survive in the sea any more than freshwater fish would. Salt works by osmotic action, essentially dehydrating the organism which is how it has been used to treat parasites for many years.
Copper will kill most aquatic invertebrates but is notoriously difficult to remove completely and so if possible I'd avoid it in a  tank intended for shrimps. In a fish tank, unless breeding was planned, I wouldn't worry about hydra.

50 litres of water weigh 50kg. 0.5% of 50kg = 0.25kg, ie 250g

Dissolve 250g salt in a bit of tank water removed from the tank, then pour it back into the tank.

Leave it in till all the hydra is dead then a couple of days longer unless Richard's book says different.

You get it out of the tank by water changes. A 50% change will get rid of half of the salt. Another 50% change will get rid of half of what's left ie a quarter of what you added, so you'll have removed 75%. A third 50% change will get rid of half the remaining quarter ie an eighth of the original so you'll now have removed 7/8, and so on.
Bigger water changes will get rid of the salt faster.

You can't test to see if it's all gone, you have to go by the number of water changes.



You don't have to use aquarium salts, ordinary table/cooking salt will be fine.

I did scrape the hydras off the viewing pane and cant see any atm. I'm going to visit my sister for a few days tomorrow and don't fancy relying on the son to keep an eye on things until I get back, so I'll have to do it when I get back.

Thanks all for the advice I  will update you asap.