Just thought I might chime in. I work in an aluminum extrusion factory with an anodizing line, which is basically a water and liquid chemical based line that puts a coating on the aluminum extrusions. In our various tanks we use these small metering pumps to add whatever chemical that the tank gets in precise dosages. We had several old ones lying around so I asked my boss if I could have one and he let me. It's called a Flex-Flo electric metering pump and it is adjustable from about 1 gallon per day all the way up to 74 gallons per day. All I do is stick one of the hoses in the bottle of bleach and the other I have got going into my skimmer. I have it turned down as low as it will go and it will empty a 96 oz bottle of bleach in about 16 hours. I was actually surprised at how well it works. It is very heavy duty (made for sulfuric/hydrochloric acid use). I have used it for the last 2 seasons and have been very pleased with it.....

And best of all....it was free!!