the AWC - how it works!

Lets say you have a 275l system and you want to do a 10% water change, you hook on a 28l AWC and set it running. Now you have 303l system with 28l of it being fresh. Now once its all mixed you have added 10% fresh water to the system and also in the AWC. When you take the AWC off you take away 90% old water and 10% new water leaving almost 10% fresh water in the 275l system! - simples!

The container doubles as a place to mix the salt and RO. The unit when used at room temperature requires no heating as the new and old water are mixed slowly during the exchange meaning there is no appreciable change in water temperature within the aquarium.

Note: should there be a large temperature difference then inclusion of an aquarium heater is recommended whilst mixing the salt solution

It is not just temperature though; all the parameters including pH are changed slowly over the course of the water change meaning no sudden shocks to coral or fish. As well as meaning all the equipment in the aquarium can be left running as there is no change in water level within the aquarium. This hands out approach can only be beneficial to livestock.

A 28 ltr container will do a 10% change on a 275 litre system. The 2.5 litres of new water that will be disposed of when the Automatic Water Change Tank is disconnected is a fair trade when all the benefits of the system are taken into account.

TO SUMMERIZE:

there are 2 parts, first is the salt mixing and the second is the water change, the salt mixing doesn't need explaining 

regards the change you are adding the volume of the awc to the volume of the tank, mixing the two and then removing the volume of the awc of the mixed water, in essence you are losing a very small % of your new water as a result but the gains far outway this loss
to give an example a 275 litre setup using the AWC28 would result in a 10% water change and result in wastage of approx 2.5 litre of your new water

whatever way you do your water change you are still mixing old and new, this method means you are mixing first (slowly) so less shock to the inhabitants!

one final note... here is a comment from a customer

"Hi Gordon, I know you calculate old new water ratio and waste to make things simple, but IMO it gives the idea that water is wasted when in reality all water is mixed and there is no such thing as old and new water. Whenever I have explained the reefloat to people in have always done it in terms of nutrient reduction or element replacement. For example 100 litre tank with 10 ppm nitrate and a 10% water change reduces it to 9ppm while using a 10% water change using a reefloat reduces nitrate to 9.1ppm."