Reconstituting aquarium water

I've been thinking about the reconstitution problem from an automatic water
changer perspective.  

If I were to build another auto-changer, I'd make a system with an RO input
(maybe a pump feeding water from a toilet tank to the RO unit, and letting
the waste from the RO go back into the toilet tank), running at maybe 10%
of tank volume per day, and a loopback siphon overflow output (or a drilled
tank output).

Since I'd be using RO water, there could be a problem with overly soft

What I'm thinking is to put an in-line cartridge between the RO unit and
the tank and fill it with limestone and dolomite chips.  Some of the
limestone and dolomite would dissolve into the RO water as it passed
through and enter the tank system, later to exit the tank via the overflow.
This would not have the same effect as putting limestone or dolomite
directly in the tank, because the tank water would not continuously
circulate over the carbonate rocks.  

However, this is another, simpler alternative.  Since I'm already doing a
continuous water change, placing a small amount of limestone and dolomite
directly in the tank might have the same effect and keep the water from
becoming too weak.


David W. Webb           Enterprise Computing
Texas Instruments Inc.  Dallas, TX USA
(972) 575-3443 (voice)  MSGID:       DAWB
(972) 575-4853 (fax)    Internet:    dwebb at ti_com
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