Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
1. Should I invest in an RO unit or buy water from a store? Is it worth it to buy your own system? I know there is the initial purchase cost and then you have to replace 1 filter every year and something else every 2 years? Any more hidden costs I'm missing? (I know about the waste water...was thinking I could use for laundry maybe?)
If you have only a small tank, then buying a few bottles from the store is probably OK. But a larger tank, or several tanks will take a lot more water and it is much more cost effective to have your own unit. Filter and membrane replacement schedule is more a combination of what you are removing and how much RO water you are making. Get a TDS meter and monitor the water. When the TDS starts rising it is time for maintenance.
Not sure about doing laundry with the waste water, but it is OK to irrigate the garden with it.
2. Do I just add the Seachem Equilibrium to the RO water or should I also be adding other dry ferts for my plants in addition to the Equilibrium... or instead of the Equilibrium?
Depends on what sort of water you want to end up with.
Seachem Equilibrium has potassium, calcium and magnesium, plus a very low level of a few other minerals. It is basically a source of the minerals that the fish and plants need that we measure as GH. (The calcium and magnesium are GH) There might be enough potassium to help the plants some, if you are running a low tech set up, but I just added ferts, including K, even in tanks where I was adding Equilibrium. Plants will need nitrogen, phosphorus, potassium, iron, calcium, magnesium and traces. Some of this will come from fish food and Equilibrium, but I would be prepared to supplement with plant fertilizers. I also add baking soda for the carbonate. The amount depends on what pH the fish want. 1 teaspoon per 30 gallons adds 2 dKH. There are other sources of carbonates, for example potassium bicarbonate, if you do not want to add the sodium from the sodium bicarbonate (baking soda).
3. Anything else you can tell me about using RO water?
Make the change slowly. Top off with pure RO, but when you do the first few water changes make the new water a blend of RO + well water. Then a few more with a greater % of RO in the mix. It may take a month or longer to get the water in the tank in better shape, to get rid of the largest amount of the well water.
Once the GH, KH, TDS is where you want it, but maybe you suspect that there is still too great a % of well water in the tank you can do larger water changes, always making sure to adjust the RO to the right mineral levels.