A little about automated water changes
As I mentioned, in an earlier post, I changed out the equipment I use for automated water changing. I replaced the Masterflex perstaltic pump (dual heads) with my LiterMeter III and one remote LM pump:
The LiterMeter w/remote pump works really well for water changing. I have a 65gal reservoir tank that I use for saltwater mixing. You can see it here:
I decided on an 10% water change per week - a little less than 18 liters per day - so I set the LiterMeter accordingly:
Approx. once every 12 days, or so, (when the saltwater storage tank is empty) I set the LiterMeter to OFF, and turn a valve allowing RO/DI water to trickle into the tank. The water stops when a float valve is activated - takes about 9 hours as I have a double 75gal cartridge RO - at that point I turn the RO valve to the off position. Then I dump in a 50gal bag of salt (there's always 10gal left in the tank when I start filling), I turn on a circulation pump to mix the water - I let it run until I feel like turning it off. After the water's mixed, I set the LiterMeter to RUN. It changes about 4.5gals each 24 hours.
So all that's required for continual water changes is, every 12 day, set the LiterMeter to OFF, turn a valve ON, turn a valve OFF, dump in a bag of salt, turn on a pump, turn off a pump, and set the LiterMeter to RUN. That's it - the whole thing (other than RO fill time) takes less than 5 minutes.
The beauty of doing changes this way is that because the small amount of water being removed/added, at any given time:
1. temperature of the new water is not a concern - too little is being added at any given time to cause a change.
2. specific gravity is normally never affected. If it changes, due to too much or too little salt in the mixing tank, the change will be very gradual (1.026 > 1.025 for example) over a period of days - this can be very easily and safely corrected.
All in all, I've found that this method makes for very stable temp and SG conditions.
The LiterMeter removes water from the overflow section of the sump and sends it to the main drain. The new water goes to the return section of the sump.
BTW - Some may wonder about the efficiency of doing continual water changes. Aren't you immediately changing out some of the NEW water with the OLD? Let me quote a small part of an RKM article from Randy Holmes-Farley:
"These changes are slightly less efficient than single batch water changes of the same total volume. A continuous water change of 30% exactly matches one batch 26% water change. As with very small batch water changes, these have the advantage of neither stressing the organisms (assuming the change is done reasonably slowly), nor altering the water level in the aquarium. The ease of doing such changes automatically also makes it far more likely that busy or lazy aquarists will actually do them."
For those interested, here's a link to the full article:
Water Changes In Reef Aquaria