What is the best RODI unit from Bulk reef supply?

Best bet is to call them and let them know what you situation is and what your planning to do with the system. They'll get something that matches your needs. Better than getting something you think is working great then finding out you should be running something totally different.

 

http://forum.marinedepot.com/Topic25081-13-1.aspx

 

Here are some things to look for in a good system for this hobby:

No more than 4 stages (sediment, carbon, RO, DI) unless you have specific water quality issues you want to address
Standard-sized prefilters, membrane, and DI cartridge
Brand name, high-rejection membrane
Specifications provided for each stage
For typical tap water: 1 micron sediment, 0.5 mic carbon block
Pressure gauge after the prefilters and before the membrane
Thermometer
TDS meter (handheld or in-line)
DI bypass
Vertical DI stage
Refillable DI cartridge
Aluminum bracket
Quick connect fittings
No water from pressurized storage container delivered to DI
Flush valve
Clear housings
High-quality instructions written in clear English
Customer support before, during, and after your purchase
A vendor involved in your hobby

 

+ 1 on the instructions written in English, and proper English would be another bonus.

 

the 5 stage is what I install for a mass majority of my customers that I have done custom tanks for. It works great for the average amount of water you will be making. But ya add a float valve and I also suggest the pressure gauge