Restarting tank after disease outbreak

[tolstoy21]

I've had a 125G running for some years now.  In the past year+, fish have been dying off, one at a time. Typical symptoms are progressive bloat (no pine coning) and red patches on sides or belly.

I maintain a lot of tanks, and this is the only tank that I've had any systemic illness in. I'd like to just move all the fish out, take out plants and decorations, and start anew. However, i don't want to nuke this from orbit.

So, if I want to keep the substrate and try to maintain the current biological filter to a degree, what are my best options, if any?

Should I dose the whole tank with salt and let that run for a week+. Will a salt treatment and 2 or so weeks without fish kill off any pathogens / parasites effectively to reintroduce fish? Will salt affect the beneficial bacteria?

I've heard this suggested in the past and was wondering is anyone has had success with this.

Theoretically, I could also ad a UV sterilizer to the tank (I have a large one sitting unused), but I'm a bit reluctant to hook it back up because it needs a replacement bulb and Im feeling lazy.  

Any tips, aside from empty it out and scrub it down (cause I know I can do that if needed) would be appreciated.

I'm basically trying to avoid having to remove and replace substrate and re-cycle the aquarium. Plus, if I were to sterilize it by manually washing, this would include overflows, plumbing, check valves, sump, etc. And that's a lot of work.

[ndfi78]

Someone like @Colu would have a better answer, but I would think that you would want to a longer period than 2 weeks. I've seen people say a month before, but that was also with draining and drying the tank. I don't know if keeping the tank full would extend that. 

[Guppysnail]

I’ve always heard 1-2 months running no inhabits is good. I’m a nuker so have never done it.  I don’t know how shortened this would be with salt. I think it should be shorter but not sure.  

[Colu]

Most pathogens and parasites won't survive longer then 30 days without a host you can use a very high dose of salt 5 table spoons for 1 gallon let that sit for 30 days or you can do a 3% hydrogen peroxide solution to steriliser the tank  you can add it directly to the water and leave your filter running after a couple of days it will break down into H20 and oxygen gas and then leave it empty for 30 days I would also take out and sterilise all your filter heater decoration in the tank as well before reintroducing fish

Edited April 27, 2022 by Colu

[dasaltemelosguy]

@Guppysnail and @Colu, could @tolstoy21 just operate his tank without inhabitants for 30 days by feeding 2PPM of ammonia a day to keep the BB alive? ...effectively performing a redundant fishless cycle but with the end that in a month's time, the pathogens expire from no hosts, but the BB would be ready for action. Could that work? 

[tolstoy21]

Thanks everyone. I guess I'll just nuke this thing form orbit and start anew. I'll just circulate some bleach solution in an empty system, then flush that out and dose heavily with Prime.

I'll grab some media from another tank to jump start the cycle.

Really, I was just hoping to not throw out a ton of Flourite Sand substrate.  But it has many years of fish doo-doo in it, so I should probably just let it go.

I was also hoping to avoid all the various diatom and other algae phases associated with a new tank. Those are the most 'not fun' part of the hobby.

Edited April 27, 2022 by tolstoy21

[Torrey]

On 4/27/2022 at 8:14 AM, tolstoy21 said:

Thanks everyone. I guess I'll just nuke this thing form orbit and start anew. I'll just circulate some bleach solution in an empty system, then flush that out and dose heavily with Prime.

I'll grab some media from another tank to jump start the cycle.

Really, I was just hoping to not throw out a ton of Flourite Sand substrate.  But it has many years of fish doo-doo in it, so I should probably just let it go.

I was also hoping to avoid all the various diatom and other algae phases associated with a new tank. Those are the most 'not fun' part of the hobby.

I have typically found that the H2O2 method doesn't trigger the algae stages of new tank syndrome. Probably would salvage your Flourite substrate, as well. You would still need to reintroduce BB from an established filter in a different tank, but if you are willing to run it empty for a month after pouring in the H2O2, it should be clean, safe for new inhabitants, and able to bypass the awkward teen stage of diatom==> dust==> hair algae.😁