Question about PH and KH

[LittleMossHead84]

I read on one website that ideal levels for a planted tank are PH 6.9 and KH=4? MY Ph is at 6.4 which on another website says it perfect if around 6.5? Then I am stuck wondering if they are using the high PH test results or the regular Ph test results. Thoughts?

[jsoong]

pH is pH, no matter what test you use, it should be the same. The different kits & range have differing accuracies, but pH is a physical property of the water that you are measuring.

Are you reading about planted tanks with CO2 injection? This is a totally different discussion as to what water parameters is best suited to a planted tank. <And they should be talking about CO2 level, which is a function of both KH & pH (plus other things), simply mentioning a pH value doesn't mean much ....>

Assuming that you are NOT injecting CO2, there are 2 competing factors in deciding what is ideal water for a planted tank:
1. You would want a slightly acidic pH (ie high 6's to 7.0) so the plants can get at nutrients (esp. iron) easier.
2. You want a reasonable KH (at least 2-4) for pH stability for the sake of the fish.

However, in the typical carbonated buffered water, the KH is linked to the pH. If your KH is 4, your pH should be 7.5. The 6.9 pH with KH of 4 requires artificial CO2 injection to 15 ppm. <Those numbers are actually really good for plants, but requires a high tech setup.>

For most people, you are best to stick with the water you have. There is no point chasing some mythical "ideal" pH or KH. <If you are injecting CO2, you should aim for a CO2 level of 15ppm. This will cause a drop of the pH, the actual final pH depends on what your starting pH & KH is. So if a site say pH of x is good for CO2 injection, without taking anything else into account, that would be wrong.>

[timwag2001]

most plants dont require a certain ph, but are ideal in acidic water.
some plants like tonina require a certain ph and kh.
but the average plant will be fine in your water

[ricardo48]

Yeh my tapwater is 8.3 ph KH of 14 and I have grown a wide range of high light plants succesfully now. With and without co2.

My PH is now currently 7.2 and kh of 14 so about 30ppm co2.

[Blueiz]

If you use the ph high test kit and it tests at the bottom of the scale, you need to use a reg ph test kit to get the true reading. This works the same as if you use a reg ph test kit and get results on the top end of the scale, you need to use the ph high test kit to get a true reading.

I successfully kept a fully planted tank with a ph of at most 6, as well as many fish. I don't think your ph will be of much concern where plants are involved.