Using Only RO Water

[DJW]

When I discovered that my well water was at 45ppm nitrates, I plumbed a RO system and drain at the back of the tank. I turn a valve in the morning that starts dribbling RO water into the tank, and leave it on all day. That's about 22 gallons per day of incoming RO water in a 90 gallon tank (its actually 30 gallons but a mix of old+new is flowing out the overflow, resulting in 22 gallons of fresh input). That part is easy, but I have been concerned with having the TDS and GH too low. To re-mineralize I have been running a simultaneous IV drip of dissolved Equilibrium to keep the GH up to 2 or 3. Although KH is only 1 or 2 the pH seems to be steady at 6.6 or so. TDS hangs around 60ppm.

How much hardness or GH do you think is enough for good health. I suppose the plants will want at least 3 but the fish I'm not sure about. The IV drip is a hassle and so if I can get by with less addition of minerals it would be simpler. Obviously until I can figure out why the well is polluted I'm going to be keeping mainly Rams, Discus and Cardinals.

[israelillo81]

you should not worry that much, i have keep my adult discus in pure RO for prolonged periods of time. Its a bit serious for juvenile fish that are still developing. The juveniles can grow with deformations due to lack of trace elements

[DJW]

I got out of aquarium keeping for 30 years, and I never expected to have water that was unusable. I discovered the nitrates in the well water after cycling a tank. I kept changing more and more water and saw no drop in the nitrates. Now there is about 60 gallons per day of RO flowing in, and I'm testing every day to see how it goes. I did read elsewhere that juveniles need minerals. The hobby has changed a lot since the 80's and I'm learning a lot lately.

[MadMatt]

The only thing I could see is ph swings if there isn't enough buffering.
Your putting minerals back into the water so your good.
Just watch your ph swing.


When I discovered that my well water was at 45ppm nitrates, I plumbed a RO system and drain at the back of the tank. I turn a valve in the morning that starts dribbling RO water into the tank, and leave it on all day. That's about 22 gallons per day of incoming RO water in a 90 gallon tank (its actually 30 gallons but a mix of old+new is flowing out the overflow, resulting in 22 gallons of fresh input). That part is easy, but I have been concerned with having the TDS and GH too low. To re-mineralize I have been running a simultaneous IV drip of dissolved Equilibrium to keep the GH up to 2 or 3. Although KH is only 1 or 2 the pH seems to be steady at 6.6 or so. TDS hangs around 60ppm.

How much hardness or GH do you think is enough for good health. I suppose the plants will want at least 3 but the fish I'm not sure about. The IV drip is a hassle and so if I can get by with less addition of minerals it would be simpler. Obviously until I can figure out why the well is polluted I'm going to be keeping mainly Rams, Discus and Cardinals.