Chiefzod:
I do small batch water changes using the doser. 3.5 gallons in and 3.5 gallons out each day, for 15 days, mix up a new batch and repeat.
Here's an excerpt:
Small batch water changes: These changes are similar to the large changes above, but are much smaller and are done more frequently. Daily changes of 0.25% to 2%, for example, can be used. One could also do a series of consecutive small water changes on the same day. This method ensures that organisms near the top of the aquarium are not exposed to the air, and that water parameter shifts are less sudden. These types of changes can be done in a variety of ways, such as by removing water via a skimmer and replacing it once a day, or by simply taking out an amount (such as a half gallon) and replacing it once a day (automatically or manually). While lots of smaller changes (say, 30 changes of 1% each) are slightly less efficient than one larger one (30% in a single batch), the difference is small (30 changes of 1% each exactly matches one 26% batch water change), and consequently other factors of convenience or stress on organisms may be more important.
In doing batch water changes of 2% or less, aquarists need not particularly worry about the changes in the water parameters that will result, as long as the new water is of reasonable quality. For example, a 1% change with new water at 55°F from a basement reservoir will change the aquarium temperature only from 81°F to 80.74°F. Differences in salinity are also unlikely to be significant.
You can find the whole article here:
http://reefkeeping.com/issues/2005-10/rhf/index.php#12
I just use two dosers to accomplish this and I change approx 100 gallons - 1/3 system volume -- every month with NO STRESS from temperature, salinity differences, etc., and it replaces all the trace elements on a daily basis. I have my third doser topping off the tank. I just consider the amount of top off and set the doser, usually in the summer and in the winter, as it differs in amount.
I've also used the level probe for top off, which also works well and there is no change in salinity as it all evens out by the end of the week when I test.
Check it out.
George