RO/DI Waste Water

[dwall174]

I recently set up a 38 gal African Cichlid tank mainly because I was told that the waste water from my RO/DI unit that I use for a Reef Tank is ideal for Africans. Anyway I’m just wondering if anyone that also uses an RO for either Discus or Saltwater has tried this?

I haven’t got a GH hardness test kit yet! I originally thought I could use my Salifert KH kit? But I guess Carbonate Hardness KH/dKH is different than DH or GH? Anyway I have been able to keep the PH around 8.0 & the Carbonate Hardness/Alkalinity is 7.0 dKH or 2.51 meq/L Temp is 78 degrees! Is there some type of conversion table to convert the Salifert’s kit reading of KH Value in dKH or meq/L, into the GH or DH scale?

[SnakeIce]

depends on what is in the water. some older houses still have copper pipes and the waste water would have higher levels of copper for example.

I would check with your water source or have your water checked for nasties that you wouldn't want consentrated in water that would be used for a tank.

I'd trust the buffering from crushed coral quicker than I would concentrated tap water. but if things check out ok I would use it.

just my 2¢

[Z Man]

I have been using an RO unit for well over 12 years now. My tap water is 175ppm TDS. The so called "waste" water comes out around 180ppm. There is not that much difference between my tap and "waste" to make a difference. Almost all the dissolved solids are collected in the filters and not transferred to double the hardness of the original supply. I have no idea where that idea started.
P.S. The pre-filter removes most if the sediments that are in most water systems so we use the "waste" for drinking & cooking. I tested my "waste" water against the bottled water my neighbor has delivered (and pays a high price for) and mine came out much better in all the tests.

[dwall174]

I'd trust the buffering from crushed coral quicker than I would concentrated tap water. Yea I have about 50lbs in a sump with an UGF just for the buffering!


Almost all the dissolved solids are collected in the filters and not transferred to double the hardness of the original supply. If that was the case your TDS reading would be much lower on the waste water than the inlet water?

My city water is pretty good at only 125 TDS & the waste water is not much different at 135 so it’s not really adding anything much as far as TDS! However being that it’s already ran through the sediment & two carbon filters there would be no chlorine in it. The way it was suggested to me was that the waste water along with the crushed coral would be close to what the Africans preferred.

[Z Man]

No as the first filter just removes any particles that are in the water (which we can't see). As a matter of fact, mine has 2 filters BEFORE it goes through the RO membrane. The first 2 act the same way one of those faucet attachments work to remove particles but then then 2 lines come from the RO membrane where the Oppm and "waste" water is collected.