Sealing a fish pond

Well I know this is sort of off topic, but when I returned from my trip (and I had a great time!) all the fish were in these big rubber maid tanks and the pond was dried up. After over 30yrs it decided to start leaking. Its a concrete pond so I was thinking of using something like a swimming pool paint/sealer. Anyone out there know anything about concrete pools and ponds? These fish cost between $500 and $2K so I don't want to use something that will kill them when I put them back in. Any ideas would be greatly appreciated :(