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disease outbreak - Making a tank safe again?


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So I think I may have the start of disease outbreak in my tank (I think it could be columnaris). Although only one fish has died and the others look fine, its only been a day. Backstory: I've been QTing new fish in my very nicely planted tank that I had been establishing waiting for an expensive betta to arrive. I realized now that was dumb because with a fish dying I'm terrified whatever could still be around for when the betta comes... So whether this is columnaris or something else I need to know how I can disinfect the tank or what I can do to make sure its safe sometime down the road for the betta. 

So far my plan is to set up a third tank somewhere and start cycling a sponge from my healthy tank to have ready for the betta that will be here in two weeks. But if all the fish die in the "QT tank" or if the other fish live what can I do to disinfect it for the betta eventually?

Also this tank has a lot of plants in it, deep sand substrate, and lots of snails (mostly MTS, but also a few nice nerites that I really like) with sponge filters. I don't really want to have to tear it all apart or harm the plants or snails. 

Plants I'm worried about are: java ferns, banana plant, anacharist, dwarf sag, a struggling jungle val, and some sort of sword I think? 

Tank survivors thus far: 2 Guppies, 1 corydora, 5 anchor cats, nerites (I could technically return the nerites still). The anchor cats were supposed to stay in the "QT tank" with the betta and everyone else is supposed to go into my 29 gallon with the other schools. 

If all the fish die, could I leave it set for two months and everything be okay? or could the snails harbor something? I also considered dosing with hydrogen peroxide and/or salt, but what levels would be safe for the plants? 

If fish live, how long should I QT for until deeming them safe to move to my other tank or add the betta too?

Edited by SMiCay
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To make sure your future betta tank is parasite free, once all the fish have left the tank simply leave it up and running for a week or two. The parasites will die off in a few days without a host. I would say stop treatment once fish stop showing signs of parasites. Treat again for another week a week later to kill off any eggs that hatched from the first parasites. I don't think using hydrogen peroxide or salt is necessarry. I don't think (and forum members mistake me if I'm wrong) the snail will be carrying the FISH parasite because most fish parasites are specific to its host. Just like a human parasite wouldn't go live in a cat. 

I usaully quarintine my new fish for 4-6 weeks before deaming safe and putting them in my display. All though because it sounds that you have had these fish for some time now, once they have passed there full treatment of parasitic medicine it should be fine. 

Here is a video cory did on this topic. In this video they reccomend either draining the tank (which isn't exactly an option for you) or just runing it with water with no fish. But he also talks about the options with salt and bleach.


Edited by James Black
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