I am in the UK and I have a couple of Reefloat products; Auto water change (
http://www.reefloat.com/index.php/awc28.html) and Auto top off (
http://www.reefloat.com/index.php/atu-pro3-36.html).
Gordon who build these units has a good reputation here in the UK, and I have found them to be very reliable. I got the auto top off unit first, for my Reefer 350 which has a top off tank at about 10 litres and would need refilling in 3 days. So I got the ATU 36 which sits very nicely in the right compartment and it feeds the Reefer top off tank. Reefloat has since released a optical water level sensor mount that can be fitted in place of the Red Sea float switch. I have this but I haven't fitted it yet, the Red Sea float switch does get stuck once every few weeks so I keep meaning to do the modification.
More recently I got the AWC unit which is also very useful. Note that the concept is that the unit will pump fresh salt water from the bottom of the container through one hose, and existing tank water is simultaneously siphoned out into the unit from the top. This is on a timer which runs for 60 seconds on and 60 seconds off, and is preset according to the size of the unit. So my unit runs for about an hour. Since there is only your tank, the AWC unit and there is not a 3rd vessel, there is some mixing of existing tank water and the fresh salt water within the AWC unit once the pumping/siphoning starts. But I am very happy with it, this allows me to do weekly water change, I just put fresh RO/DI water in, weigh out and pour in the salt (Red Sea Pro so dissolves in about 2 hours with occassional stirring without needing to constantly mix), wheel the unit to the tank (I have it strapped to a small folding wheel cart), put the hoses in the tank, plug in the power supply, check that the pumping/siphoning starts and nothing is leaking, wait for the preset time to elapse, wheel it away, empty the container, quick rinse with RO/DI water and light brushing every couple of weeks if there is visible residue build up inside. It doesn't bother me that it is not a true 28 litre water change in the sense that it does not first take out the 28 litres of existing tank water and put in 28 litres of fresh salt water.
Cheers, Wilson
