How to automatic mixing water

[wolf_bluejay]

Originally Posted by sphelps

I don't think it's reasonable to assume most can store 200 gallons of water, I've seen a 200 gallon poly tank and it's big and I can't see many people finding a convenient location for it. Some would even have trouble getting it inside.

Also 2 pumps could work and do work, most use dosing pumps which yes cost more than typical pumps but don't forget a controller with programmable logic and salinity control will run for at least $1000 so it's certainly not a cheaper option but I would agree it's a better one.

Well, the cost of the controller I don't think could be rolled up into, as it has other uses as well. If oyu wanted to just go with some dedicated controller, I don't think the parts would cost more than about $50+ plus the sensor.

And if you went with the "salt and fresh top-off" the salinity of the salt water would no longer matter, as the controller would always work it out in the end. So if you did go with an increased salinity salt water (4x usual) you would only need 50 gal to store the equivalent of 200 gals of water change.
In my case I have a 220 gal tank, so I'm going on the high side of things with that in mind. If you have a 75 gal tank, you could put in a 20 gal salt water tank and hold the equivalent of 80 gals of water change.
Looking at a lot of fancy water change setups using brutte garbage cans, they have 50 gals of RO/DI and 50 gals of salt water ready. having 1.025 salt water handy would eliminate the need to store 50-100 gals or RO/DI water and have a much smaller fresh water tank.

Heck, with the controller taking care of things, you could probably get away with mixing the salt water at something like 1.015 or so, and most of the top-up can come from just the one tank assuming a few gal a day water change. Top up with 1.015 water, pump a bit out, and let evaporation do it's thing.

If you didn't have the controller -- you could (in theory) mix 1.015 water, have a small pump on a timer to remove a gal a few times a day, and have the 1.015 go in as top up. if you could find the right balance, between how much to pump out, and the density to mix up to match your evaporation -- it would work with constant tweaking. I just wouldn't want to have to watch things that closely.