Is this source water good enough for use?

Last time i measure it wasn't nitrate free, tested about 5 to 10 ppm of nitrates, which is the main reason i'm doubting the filter's usage

 

The nitrates will eventually build up resulting in algae blooms and poor coral health. So an RO (even if no DI) would be much better.

As for how long to replace the filters, a RO membrane can last between 1 and 3 years, the less TDS, the longer it will last. You can also buy flush kits will can extend the life of the membrane. Depending on how many stages you have, the carbon filter, DI resin and sediment filter usually need to be replaced at least yearly. But it depends on how often you use it and what you water is like before it goes through the system.

 

And I would imagine if you tied up the RO/DI after your existing filter, those filter cartridges and membrane would last a good long while.

 

lol can't put it anywhere near there, my dad can't see it. so i'm putting it outside the house, but my tank is near the door so it's fine. they wouldn't understand the need and importance of having RO/DI water '' just for fish tank'' . The last time i used to buy bottled distilled water for my nano he was pissed.

 

hmm even with a strong skimmer and lots of chaeto? my chaeto seems to be doing a hell of a good job removing nitrates now ;D

 

Alright guys i'm determined to get the RO/DI filter for my fishes and corals sake ;D am trying to talk my mom into getting it now as i'm still a student, she loves reef stuff and adores corals. might be better talking to her, but she doesn't understand why her amway espring which looks like eva from WALL - E isn't enough

 

RO membranes last 18 months to 3 years with some brands. Its not unusual to find a Spectrapure unit with a 7-10 year old RO membrane though since they use much better quality prefilters and carbons than most others. If it never gets to the membrane it does not have to be flushed away.
Prefilters and carbon blocks are normally changed at 6 month intervals. Again better filters do a better job of protecting the carbon block so replacements can be extended if you pay attention to pressure drop and I use a small inexpensive low range chlorien test kit to monitor chlorine break thru from the carbon block. I go about a year between changes and I am meticulous about disinfecting the system while I have it apart at filter change time.
DI resin is entirely dependent on how well the membrane is working and how much water you make. Again Spectrapure tests their membranes and rejects low performers either by individual testing or batch testing. Better membrane performance better DI life.

I would be hesitant to mount it outside unless it is protected from the elements and direct lighting. Not hot or cold extremes and no sunlight. Bacteria and viruses can grow in the housings as you have provided the perfect living conditions, warm water with no chlorine residual since the carbon removes it and sunlight and you have a nasty soup. If it can go in a garage or laundry room that would be better.

Don't waste money on a flyush kit, they have no value. Its the 4:1 waste ratio that flushes the membarne continously when its in use. Flush kits just increase the velocity around the exterior surface of the membrane and do nothing but lighten your wallet.