When or if to sanitize a tank after the loss of a betta?

[Michelle]

I had to euthanize my betta, can I leave the tank running for a month or so, preform weekly water changes and have all the "whatever needs a host fish to live" die off? What should I do before it's ready to house new fish, thinking about substrate and plants in there (java fern, stem plants and moss ball) as well as it housing the same sponge (in hopes of keeping it cycled) in the HOB filter. Should I sanitize everything in bleach solution and rinse the substrate or throw it out?

Here's the history of the tank and betta below if it helps. 

I had a betta that developed a moldy ventral fin, I added "tetra all in one" tabs, I think two, but stopped after and kept up increased water changes and it was all looking good. A few weeks would pass and saw maybe only 4 ich spots or so show up, I preformed water changes at the sight of anything and we were back to normal and what seemed healthy. Then some time passed and he was at the bottom of the tank breathing really heavy, tested the water all was good, no ammonia, no nitrites and super low nitrates, but did a water change added aquarium salt.. after some time that did not resolve and I had to euthanize, heartbreaking. Now the tank is running with some plants, a moss ball and fluval stratum. I syphoned all the water out (as low as I could) and added fresh with prime of course. I'll add that my fear is that I introduced something to that tank from another when adding a plant. I had gotten a sick glowlight tetra, breathing super fast since I got it but stayed like that for weeks, looked maybe malformed, I never really knew. I've since euthanized that fish in fear of other inhabitants in the tank (this is a separate tank), but all other fish have been doing well for some time. Maybe my betta was old and low immune system (don't know the age we were his third home).  Should I be scared of fish TB (possibly from glowlight tetra infecting both tanks), or unlikely the case?

Thank you for reading, I've tried to learn as much as I can and I don't want to be too stress out that it turns me off fish keeping. I really appreciate any input. 

 

[HardeepTheLondoner]

You could keep it running to achieve die off, but that’s not a guarantee. If it was me, I’d probably drain the tank and let it sit dry for a few days. Then I’d go 50:50 Bleach and water and then throughly rinse the tank out with water to dilute any bleach.

Don’t worry about your plants, they are all very forgiving and won’t mind anything for a while. Just keep them wet and get them some light if possible but don’t worry if you can’t.

Also, you’ll probably lose your cycle when you strip the tank down. I’d run it in your other tank for a week or two to get it seeded again and then slowly add small amounts of fish.

[Michelle]

What about the substrate, is rinsing enough since it's so porous? Do I do a part light peroxide or bleach quick bath for plants and moss ball? Thanks so much I think I'd rather be safe and take the tank down and give a good clean like you said. 

[HardeepTheLondoner]

I’d just rinse the substrate out like normal and then put it back into the tank when setting up. When I had planted tanks, I always used peroxide at 3% strength as a dip for quarantine.

After you’re confident everything’s okay to go back into the tank, set it up and dose peroxide. After 24 hours, that peroxide will become Oxygen so it would be harmless to inhabitants once they go into the tank.

[Michelle]

Thanks so much for the help.

[ChefConfit]

Don't bleach your tank.

It sounds like a fungal infection followed by ick just wore the fish down. Treat it with salt then when you restock quarantine them in the tank with the med trio. 

If you bleach it down not only do you guarantee you kill all the BB and have to restart your cycle but you run the risk of harming the next inhabitants if any isn't rinsed away. 

[Kat_Rigel]

10 hours ago, Michelle said:

can I leave the tank running for a month or so, preform weekly water changes and have all the "whatever needs a host fish to live" die off?

This is what I would do. It seems a waste to do all the work of tearing it down when a month of no fish around achieve the same result. However, I do not speak from experience, only from what I have read. (Last time I had a tank infected, I broke it all down and took a break from the hobby.)

If you're too nervous to do the sit and wait method, I would recommend breaking it down, tossing the substrate, cleaning the tank and decor with a diluted bleach solution. Just use extra dechlorinater and let it run for a while before adding fish (which you'll need to do anyway to ensure your tank is cycled properly.) Don't forget about sanitizing nets, water change tubes, buckets, etc if that is the direction you're going.

[Maggie]

If you leave the tank set up, maybe turn up the heat to 82 for a week or so to speed up the ich cycle and ensure no stubborn "unhatched" cysts remain.