My well water is pH 7 and KH 8.

Something's wrong. With a KH of 8, your pH should be 7.8, or thereabouts.

Have you added anything to your tank -- something to try and change the pH,
maybe? Or is anything being added to your water? Water softener or something?

Supposedly fish can only tolerate about 20 ppm CO2. Is this
true?

20 ppm is a safe level to aim for. Test kits are not always super-accurate,
and CO2 levels can fluctuate throughout the day, so it's a good idea to be
cautiuos. But you can raise your CO2 as high as 35 ppm without harm to the
fish.

I don't understand how one could have a soft water tank and CO2
addition, since it would be so hard to stay above 20 ppm. Am I
missing some vital piece of info?

A soft water tank and CO2 injection can be tricky. A lot of planted tank
keepers add calcium carbonate to their tanks, if they have soft water, to raise
the KH.

I would like to get some algae eating fish--the algae is gaining on me
now--but it seems that otocinclus wouldn't take such hard water well.
Is this true? My tank is only 29 gallons and I dislike plecos . . .
any suggestions for me?

Otos would probably be okay. Most fish can adapt to a wide range of pH and
water hardnesses.

But they aren't the best fish for cycling a tank, so make sure your tank is
stable before adding them. That includes the CO2 levels.

I don't think you really had 130 ppm of CO2. Either your test kit is
defective, or there's something in your water that's skewing it. Test kits are
only good when they're fresh, so it's best to buy them from a large store with
high turnover.



Leigh

http://www.fortunecity.com/lavender/halloween/881/