Used tank that needs cleaning
Due to moving this past winter, I had to take down my tank without much time to prepare or clean the tank for winter storage. Most of the fish were caught, bagged and returned to the store the day before the move, however I was taking some of them with me to put in a smaller tank I set up at my new house. This meant that I needed to keep the tank running until the actual morning of the move.
After I loaded the rest of my stuff into the moving truck, I captured the fish I was taking with me, drained the tank and filter, removed the decor and substrate and then immediately loaded the tank onto the truck. Unfortunately it went directly into storage without even being able to give the tank a good scrub down or rinse beforehand.
This spring I took the tank out of storage to use for an outdoor summer project, only to find it covered with dried on algae, calcium deposits on the sides of the tank and hardened clumps of sand that wasn't removed during the breakdown of the tank.
If I had put this tank in a yard sale as it was, most people would have walked right on by thinking that it would take way too much time and effort to clean. However they would have been walking by a great opportunity to get a perfectly functional tank at a greatly reduced price.
Cleaning a Used Tank
One of the most effective way's I have found to clean a used tank is to use ordinary white vinegar and let time do the hard work. The vinegar is acidic enough to kill any residual pathogens that may still reside in the used tank and break down or loosen any calcium deposits that may have been left on the glass while any vinegar residues left behind after a thorough rinsing wont do any harm.
To start with, I placed the tank on the stand. I then set up filter with the sponges and some filter floss so I could clean the filter out at the same time as I cleaned the rest of the tank and it provided water movement within the tank itself. I then added 8L of the least expensive white vinegar I could find to the 300L tank and proceeded to fill the rest of the tank with water.
After the tank was filled, I primed and turned on the pump and walked away from the tank for two days (I could have cleaned it after one day but I was busy and didn't have time so I waited an extra day).
When I finally got around to giving the tank a scrub down, I used a razor blade tool for scrapping paint off of a surface to clean the glass.
paint scrapping tool
I was careful not to touch the silicone with the razor so that I wouldn't damage it. The dead algae and calcium deposits came off very quickly and easily. In order to clean the silicone areas I used a kitchen scrub pad.
After I finished scraping the tank down I let the filter run for a couple hours so that all the debris was removed from the tank. This allowed me to check over the tank to see if I missed any spots and complete any final touches needed.
Once I was satisfied that the tank was clean, I completely drained the tank and then used a hose to give the tank a final and thorough cleaning. (If you are doing this inside a house, it may be easier to use a couple buckets or watering can of clean water and make sure you rinse the sides of the tank and then drain it again.)
With the filter, it only needed a simple wipe down with the scrub pad and rinsing out the foam filters. I threw the filter floss out as it had accumulated a lot of debris.
Here is the end result:
If the tank has been stood empty for a while and has dried out then there is little chance of any waterborne pathogens surviving so there is little chance of any disease being present in the tank.
The same applies to a recently emptied tank which was well maintained and healthy.
A weak solution of potassium permanganate, bleach, saline or white vinegar all make good cleaning agents but the tank must be thoroughly rinsed afterwards.