Both are working so I shot this video to show how the two are working:
The first system has about 40 gold fish while the second (the one with a transparent window in the video) has five.
Under the second system there is also an air-to-water heat transfer and storage system. The idea is to allow the heat stored in thermal mass, water and sand, to be released slowly during the night time. This way the greenhouse temperature during the day becomes not too high and that during the night won’t be too low.
Use sand instead of soil has many advantages: it is clean, better thermal mass capability than soil, etc. The best of all, sands do not have contain weed seeds – a lot in soil. So using sands as grow media save the pain-in-the-back trouble of having to remove weeds.
The whole system is automatic. Set it and forget it. As long as the one water pump and one air pump are working, everything is fine.