Automatic-Top-Off done.
I decided to go cheap and simple on that.
RODI reservoir is a basic Rubbermaid 18 gallon bin.
I have a timer, driving an aqua-lifter pump, for a few hours/day on/off.
Tubing from that goes to a float valve, and T-s off, flowing excess back to reservoir.
So it is has redundancy : If float valve gets stuck open, slow pump is on a timer, so
will really not pump more than 2X normal water in.
While it has negative redundancy, it does not have positive redundancy.
But I am ok with that, since water level getting a bit low does not do much.
I will probably add a water level alarm to the microcontroller some day, like temp.
--
Tank is cycling well.
Nitrite has climbed, and seems to be leveling off.
Ammonia is dropping fast.
(And that is with a new test kit. I tossed out old expired chemicals)
Water is crystal clear. Bacterial bloom is gone.
Fish soon!!
Corals will have to wait a while for more stability and new lights.