For now, I use RO water from my local aquatics shop. Most will fill a container for you, I pay around $4 for 25L of water. Kind of a ripoff, I guess, and it all depends on how much water you'll be going through.
I use a 75gpd system and it's plenty and has a large reef system to support as well.
I think I am going to go with the Hydrologic Stealth 200. I'd like to hear what kind of gallons/hour people are getting when they use it in the field. Anyone who has the Hydrologic Stealth 100 or 200...how long does it take to fill your rez and what size is your rez?
Here's a list of the ones I was comparing, in case anyone else is comparison shopping...
HydroLogic: StealthRO200
$300-315
200 gallons/day
98% contaminant removal
4-Stage: Carbon pre-filter, sediment filter, 2 RO membranes
Garden hose connector & inline shut-off
8’ RO Line, 4’ Feed Line, 8’ Drain Line
Optional: float valve, extra tubing, under sink connector
SpectraPure: Eliminator 200 gpd
$299.95
200 gallons/day
Garden hose adaptor
3-Stage: Sediment filter, carbon filter, RO membrane
SpectraPure replacement filters ~20% more expensive than Hydrologic .
eBay – filterdirect: Residential RO System R05
75-85 gallons/day
$135
98% contaminant removal
5-Stage: Sediment filter, 2 carbon pre-filters, RO membrane, final inline carbon filter
Long reach faucet, pressure gauge, storage tank, shut-off valve, membrane flush feature
thefilterguys.biz: Ocean Reef Miser Six Stage RO/DI 150 GPD
$265
150 gallons/day
98% contaminant removal
6-Stage: Sediment filter, 2 carbon filters, 2 75 GPD membranes, DI housing
Garden hose adaptor, pressure gauge, drain connection
These guys do custom units so we could probably ask for one without the DI cartridge.
Air Water & Ice: The Cube RO/DI
$239.95
150 gallons/day
98% contaminant removal
6-Stage: Sediment filter, 2 carbon filters, 2 TFC 75 GPD RO membranes, DI cartridge
Choice of hose, faucet, or supply valve connection
Comes with 2 75gpd membranes which have a 98% rejection rate. For the same price you can request 100gpd membranes but those only have a 90% rejection rate.
These guys do custom units so we could probably ask for one without the DI cartridge.
Air Water & Ice: G.E. Merlin
$499.95 incl. extra filters
700-1100 gallons/day
Tubing for all connections, automatic shut-off, drain saddle
3-stage: carbon pre-filter, 2 TFC membranes, carbon post-filter
This is the time tested system for whole house RO or if you want to open up a pet shop water supply. Lots of data and field expertise available on this one.
HydroLogic: Merlin Garden Pro High-Flow
$589.95
750 gallons/day
30 gallons/hour
95% contaminant removal
3-Stage: Carbon pre-filter and 2 RO membanes
Garden hose connector & 3.8” inline shut-off
12.5’ RO line, 4.5’ Feed Line, 4.5’ Drain Line
I know Whirlpool also has a system on the market but I had narrowed by field of interest by then so I didn't look up the specifics...