Posted this in Home repair. Not sure if this might be a more appropriate
NG..?

Just moved in. Have a large in-ground, 3-pond water fountain. Each pond is
made up of a stone rim and pebble -concrete base. It apparently hasn't been
active for a few years. Once I got it cleaned out, I filled all the ponds
with water. They didn't hold water overnight. There are not any obvious
cracks, holes,etc. I suspect the concrete is porous. Is there any solutions
such as a sealer that can be sprayed or painted on the concrete base?. Was
thinking of Dri-loc (or something) for basement wall leaks...but think that
would not look right. Aside from completely rebuilding the ponds with the
proper liners...any thoughts??
Thanks
Bg

I'd try going to a store that sells pond supplies, accessories, etc and
asking them.