I just wanted to help others going to the process of deciding on which system to buy. I hope others chime in with their opinions so this thread will include enough good information so that others won't have to do as much research as I have.
I've been doing a lot of research regarding Ro
systems in planning to buy one.
I don't know how accurate this all is, but it is what I have distilled from the information so far.
The real question is, "what system is good enough for Ro
water for an aquarium?" The difference between different systems primarily seems to be in the quality of the internal filter media, and some of the connectors.
1. Prefilter (sediment filter): most offer 1-5 micron. You can get 0.2-0.5 micron as well. Basically, the lower the number, the better the prefilter. A better prefilter means less stress on your Ro
membrane. Less stress on the membrane means that it will last longer. If it lasts longer it needs to be replaced less with ultimately lower cost over time.
membrane: This is what determines your water production. You can buy membranes that filter 25-90 gpd (gallons per day). You can increase the water production by upgrading this membrane and changing your flow restrictor. You can double the rate of your system by buying a second Ro
membrane canister and filter and hooking it up in series to your existing Ro
3. Carbon block: You really only need one carbon block (if its a good one, and you have a good prefilter). Adding a second one makes the first one essentially a pre-filter and also reduces your water pressure through the system. It also increases maintenance cost since it is another filter that you will have to replace over time. They range from 0.5 micron to 5 micron. Again, smaller is better. A good carbon block also filters chloramines. It appears that if you have a system with a good carbon block and good Di
resin, you won't need a special chloramine filter setup.
resin: There is a lot of variation in quality of resins. Better systems have better resins. Again, you can buy systems with 2 resin canisters, but for aquarium needs, one should be sufficient if you have a good resin in it. (See comments above regarding carbon block)
membrane flush: You can add this relatively cheaply. It will increase the life of your Ro
membrane and decrease your maintenance cost over time. They make spendy auto flush systems that will flush your membrane every hour during use or cheaper manual flush systems that you use to flush it yourself, usually before or after each use. This is included in some systems and not in others.
Their seem to be about 3 levels of systems:
1: Bargain (ebay, etc.) : comments about these is that they tend to leak, have cheap components, connectors and high micron (less efficient) filters, high micron carbon blocks, off brand membranes and Di
2: Mid-range: I think that the BRS, filterguys, etc. mostly fit in this range. Essentially, better build quality with moderate grade filters, carbon blocks, membranes and Di
resin. You can upgrade the filters etc. when they expire to better quality.
3: Premium: This would include Spectrapure and Buckeye Field Supply. Solid build with premium filters, carbon blocks, membranes and Di
resin. The cost of their systems goes up with the quality of the internal filter components that you buy.
So, in conclusion, if you buy a better system, then your waste water ratio will be less (2:1, versus 4:1), and your maintenance costs will be less over time because your filter media and membranes will process more water and need less frequent replacement.
The question still remains, how much filtration is enough for Ro
water for an aquarium? Which system is adequate and what is overkill?
Personally I lean toward the Spectrapure CSPDI 90 GPD system which is probably overkill, but will produce more water with less waste and less maintenance cost over time.
However, I am considering the BRS 4 stage Value plus system with the plan to upgrade the filters, membrane and resin to Spectrapure products when they need replacement. Though it will have a cheaper up front cost, the level of filtration and waste ratio is "value" level (but probably adequate). I think the build quality looks good and with the right "internals" it would be a very good system. I don't like the BRS 5 stage system that everyone is so hot on, because the extra stage just makes up for poor internal media and adds to maintenance cost overtime.
That's my opinion and my thought process. I hope it helps someone.