Rejuvenating a Stagnant Tank

[MSB256]

Hi everyone. I've been lurking this site through the iPhone app and decided to sign up. Thanks for the advice you all give!

To try and make a long story short, we have a 55 gallon tank that we could not make a decision to keep or get rid of. It doesn't have any fish in it anymore, but it had live sand and live rock and has been set up for quite some time - maybe 9 months to a year. I took most of the live rock out but it still has sand.

We decided to keep the tank so now my question is do I need to start from scratch? The filtration, heater, and power head have been turned off for about three weeks. I just added 5 gallons of freshly mixed saltwater a few days ago when we decided to keep it but haven't added anymore. I would estimate there was about 45 gallons of cycled water just sitting there during that stagnant time.

 

[MSB256]

Maybe more like 35 to 40...

 

[IslandHopper]

The de-nitrifying bacteria will still be there and likely thriving!

Do a BIG water change... (certainly more than 50%) and put the rock back in (It'll need to re-culture, and the die-off on it now should provide plenty of "food" in the meantime as it re-cultures.) Also turn all the pumps and such back on.
Let it run that way for a week or two, then do another bg water change and if parameters are good, I'd put fish back in it!

(Unless everything in the tank is covered with algae at this point... in that case, it might be easier to just take everything apart, clean it with vinegar and start over from scratch.)

 

[MSB256]

Thanks Island Hopper! The rock is still good. I actually took it out and put it in a 10 gallon nano. It was just a start for the 55 but fills out the 10 nicely.

I'll do the water change and get it going again.

 

[Grizz]

Id put the rock back in fill and dose with ammonia to 4 ppm wait 3 days and test for both ammo and nitrates if the bacti are still alive they will convert the ammo

 

[MSB256]

Thanks Grizz! Good point.