Checklist:

Baking Soda - Check
A few spare buckets - check
Measuring spoons - check
Pad and Pencil - check
Calculator - check
Lab coat - Does my bathrobe count? If so - check
Maniacal laugh - will keep practicing in mirror. It's coming along nicely.

What do I do now?

Kim

*chuckle*
How many gallons does the tank hold?
What are you water test readings currently?

Greetings DataGuru!

I have Ph problems in three different tanks.

20 Gallons; established and cycled and all that. The ph problems in the tanks are suspected culprits for a sick fish. Here are today's readings: * I did treat the tank with a product called proper pH 7.0 with the water change today. It says it's supposed to buffer my tank. It didn't do anything to the ph, but it did bring the kh way up and helped a little with the gh.

ph between 6.4 and 6.6
kh 120
gh 100
ammonia 0
nitrite 0
nitrate 20

10 Gallon; this one is still cycling:

ph 6.8
kh 180
gh 150
ammonia 0
nitrite .5
nitrate 10-20

5 gallon; this one is just a hospitol tank, but the fish being medicated in it is likely a victim of bad ph, kh and gh. Here are today's readings:

ph 6.8
kh 40-80, I can't tell for sure on that one. The color's funky.
gh 75
ammonia 0
nitrite .5
nitrate 5-10

I am afraid to do water changes in this one because of the medication, but I'm going to do one tomorrow if the nitrite doesn't go away by then. The tank was completely cycled but the medication is affecting it.

Tapwater:

ph 7.2
kh 80
gh 75
ammonia 0-.25
nitrite 0
nitrate 10-20

my tapwater sucks.

I don't know which one will be easiest to fix first. I figure if I can get the formulas and calculations for the ten gallon, I can just doulbe the numbers for the 20 gallon and divide by two to calculate the 5 gallon. Does me saying that show that I have no clue as to what I'm about to do? Hahahahaha! (Maniacal laugh)

Hmmm I would have expected a higher pH with KH of 120. I'm not familiar with how the proper pH product works. Do you have plenty of surface agitation happening in your tanks?

Here's a calculator you can use to figure out how much baking soda to use based on how much you want to raise KH. It'll also let you estimate how much that'll affect pH. I usually shoot for raising pH by no more than .4 per day.
http://dataguru.org/misc/aquarium/CalKH.asp

In your 10 gallon, adding .2 teaspoon of baking soda should get you about 20ppm increase in KH (tho I'd bet KH won't go up that much cuz some of the baking soda will get used up buffering acids). That should raise pH by about .4 if your KH is starting at 40ppm. It'll only raise pH by .2 if you're starting at KH of 80ppm.

Predissolve in tank water then add slowly to a high flow area. (or dissolve in your water for the partial water change)

It might be a good idea to get drop tests for KH and pH. More accurate and less expensive.

Also consider adding either crushed oyster shell or crushed coral in a media basket or mesh bag to a high water flow area. Those dissolve when pH falls below 7.5 and increase GH (Primarily calcium and magnesium) and increase KH (bicarbonates).

You think your water is bad. Mine has 10ppm nitrates and 2.5 ppm ammonia.