If there are any locals out there you'll know that our water is not just "very hard" (240 to 300 ppm according to local water utility.) It also tastes and smells of dissolved minerals and dead algae.

I'm only planning a 5.5 gallon and with such a small tank it seems like it would be pretty simple and inexpensive to use R/O drinking water for water changes. As it turns out, in the pile of fish tank chemicals I purchased from Craigslist today, there's a jar of Kent Freshwater R/O Right. (I think I also picked up a couple of "neutral regulator" type pH-altering chemicals.)

I'm still trying to wrap my head around GH/KH vs. buffering capacity vs. pH. It's been a while since freshman chem. But can someone experienced just shoot me the basic pros vs. cons of finagling my own water chemistry vs. just dealing with what I get out of the tap? I do plan to dose CO2, which I guess complicates the equation.

The short answer is you only need soft water if you plan to keep the few species of plants or fish that require it. Or you just want to experiment like I do.

It's all very simple if you forget about pH, it's an arbitrary number when you take in the amount of factors involved with it. The goal of RO is clean water with a low TDS, only the essentials, Magnesium, Calcium and other traces to make up GH, a little bicarb if you want some buffering capacity and that will set the pH for you. You don't need anything else, your fish don't care what the pH is, rather the GH and whether it's stable, set it low for plants and SA fish, set it high for malawi cichlids etc. You can either mix Ca and Mg separate for your own ratio or just buy it premixed as GH booster from Rex Grigg or aquariumfertilizer.com.

All I do every week is add 1/8tspn baking soda and 1/4tspn GH booster to 5gl RO. I get like 3dKH, 6dGH, and maybe 7.2pH before going in the tank and dropping from CO2.

My main concern for you would be whether or not you'll find scoops tiny enough for the amounts you'll need in the 1 or 2 gallons you'll be changing out at a time. I guess you'd be premixing a bottle or two to make it easier.

I agree, it will probably be easiest to mix in big batches and then keep on hand in bottles (to eliminate evaporation) to ensure consistency.

Oi, you're right, the Kent product requires 1 tsp per 10 gallons to obtain "soft" water that it claims is appropriate for bettas. I could probably not measure a 1/10 or 1/5 tsp accurately without first making a stock solution. I guess I could get a 5 gallon bottle from the water & ice store and use that to pre-mix and store water for use in water changes.

Back when I started my first tank I gathered that fish will usually do better acclimating to the water you have vs. having to acclimate to inconsistently altered water (whether that's reconstituted R/O or just using pH drops and such.) Still though, our water is SO gross. :P If the R/O plus GH booster will work, I think that's the direction I want to go!

RO is actually better for the fish that tap being that you have consistent control over parameters long term, and the local water treatment plants can and will change things up on the fly, who knows what mother nature does to well water over time.

The GH booster from the places I mentioned is the best bang for the buck in the long run, a proven and pricey alternative would be Seachem Equilibrium, honestly it's all the same stuff which is why you can't find any info on their msds's. I guess the directions on the bottle make it worth the money but if you're testing to reach your own targets then who needs directions?


There are a lot of folks here not adding bicarb for any kind of buffering capacity, while injecting CO2, and of all the old threads here about that, no one has reported a deadly "crash". But alas I am one of the ones that still lives in fear, so I add that 1/8tspn/5gl for 3dKH and a little peace of mind, needless to say no issues. Once I get CO2 pumping strong the pH drops to 6.4 at the lowest, no further unless I have a mishap with the needle valve, in which case extra bicarb wouldn't do anything to save my fish from a CO2 overdose anyway.

It sure makes sense that I'd want some kind of buffer in there when injecting CO2, though I do respect the experience of those for whom it seems unnecessary!

Did you use trial and error to determine what dose of bicarbonate would give you that 3 degrees of KH? Or is there a calculation out there? (Again...chem was not my strong suit, LOL, it would be traumatic to unearth too much of it. )

http://dataguru.org/misc/aquarium/Ca...&pHChange=0.00

That's a cool calc.

Yes, I used trial and error, I used a tiny scooper and way too much reagent.

Yea, that calc really saved me some time (and reagent haha)