Having a bit of a problem

A lot of times the parameters look fine because the algae is using up the nitrates and phosphates as they are created. The tests can some times be deceiving when dealing with algae issues.
 
First, it's relatively normal to have periodic outbreaks of algae during the cycling period and through the first 6 - 8 months. It happens in the vast majority of new tanks. However, the algae should not consume your tank -- smaller amounts are what's typically normal. The use of RO/DI will greatly reduce the chances of having chronic nuissance algae problems. The cost of purchasing and maintaining your own RO/DI unit will be minimal compared to the amount of time and frustration a chronic nuissance algae problem can cause.

If your issues are being caused by phosphates, it is likely that your tap water is the culprit. It only takes a very small amount of phosphate to result in nuissance algae growth. Most hobby test kits cannot accurately measure down low enough to be of much use when it comes to phosphates.

The size of the RO/DI unit itself, in terms of production, is not really tank dependent. The cost difference between a 20 - 50 gpd RO/DI unit and a 75 - 100 gpd unit is so small there is little reason to purchase one with the lower production rate. 75 gpd is about the point where you can maximize production speed with removal effeciency. As posted above, The Filter Guys is an excellent source for a RO/DI unit. I buy all of my replacement cartridges and DI resin from them. Air, Water, & Ice and Spectrapure also make quality units designed around the marine hobbyist.
 
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