I keep 6 goldfish(ranging from 2"-8", not Koi) outside in one of those Iris 4x2' Christmas Tree tubs. It works awesome and a Whisper 30-60g filter fits perfectly on one of the short sides. I used a used filter from my 5 year old established tank and it cycled in less than a week, with nice green algae growing on all of the sides/bottom(and we all know that algae doesn't grow just anywhere). Fish didn't even know they had been moved and it has been so easy to maintain. I do have a bungee cord in the middle of the tub to prevent it from bowing so much and warping the tub. It holds water very well though.


If you want to keep them in a tub, it's always very possible, it just needs to be treated like a tank in respects to cycling and all that mess. Adding Prime, Melafix, and Stress Coat helped mine get through their short cycle. Definitely get a filter on that tub though, the fish can't go too long sitting in their own waste unless you do water changes everyday.

With the old tank, strip the glass of all of the old silicone, clean it with alcohol, let it dry and them slowly reapply silicone in a thick bead. Then let it cure for a good week so you know that it is set. Then test.

I hope you can get it up and running. Try the tub though and see how you can get that running, then you won't have to worry how long it takes to either seal the old tank or get a new one set up and cycled.