If you're worried about ingestion, you could partition the pool like a sandwich, laying a sheet of plastic or tempered glass under which any dissolved metals would remain. From bottom up, it would go pool bottom, Sr-90 (and others), water, plastic, water, surface. You'd still get the colour, and the heat could transfer through the partition. Then it's just a matter of finding a clear plastic that can withstand the radiation.

Did I mention that I think this idea is amazingly cool?

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