Aquaticco,
Welcome to APC! It seems that you have a good set up and it wouldn't be an exageration to say that whatever you ask on this site will get answered better than any book
Your KH and GH:
Test kits
The first thing that you must do before anything else is to verify that your test kits indeed show actual numbers. It'll probably be a hassle for you to check the kits by preparing clean solutions with known concentrations of HCO3 (KH), Ca and Mg (GH). Maybe you can just make sure that your kits are not old and also to compare the kits to a pet shop results (you could take some of your water there and ask them to test it for KH and GH).
KH
The KH is very low but I'd leave it where it is and not worry about it. Some people may say that such low KH may lead to what is known as "pH crash" - a sudden pH drop down to some very low number (3 or 2). This sudden change may cause death of fish and probably plants. However a pH crash seems to be more of a theoretical than an actual phenomenon - it seldom happens.
GH
Now GH of 17 is way out of whack. You will be better off bringing it down to more sensible levels - 3 to 6 is great, but even 9 would be ok.
I wonder how did you end up with such high GH. The first thing that comes to mind is that something in your tank (it maybe a single rock) is releasing Calcium in the water. But that would bring the KH and pH up too and that is not the case.
GH is a measure of the Calcium and Magnesium concentrations in your water. You can have GH =17 from Ca only or GH=17 from Mg only. Or mainly from one or the other. Without a Calcium test kit you have no way of knowing which one of the two elements contriubtes to such high GH. The Mg concentration is not checked with a test kit but it's calculated by using the GH and the Calcium - try this calculator.
If you don't want to get involved in testing Calcium and calculations you could try a simpler but very much blind approach. Test your tap water and if it has a GH considerably less than 17 then just do a few big (50% or so) water changes. That way your GH will go down but you will still not know the amount of Ca and Mg which are important for plant growth.
Another thing that may want to do is to make sure you check the pH more precisely. pH of "6 -7" does not mean much, usually you want to know if it's 6.1 or 6.9
--Nikolay
Welcome to APC! It seems that you have a good set up and it wouldn't be an exageration to say that whatever you ask on this site will get answered better than any book
Your KH and GH:
Test kits
The first thing that you must do before anything else is to verify that your test kits indeed show actual numbers. It'll probably be a hassle for you to check the kits by preparing clean solutions with known concentrations of HCO3 (KH), Ca and Mg (GH). Maybe you can just make sure that your kits are not old and also to compare the kits to a pet shop results (you could take some of your water there and ask them to test it for KH and GH).
KH
The KH is very low but I'd leave it where it is and not worry about it. Some people may say that such low KH may lead to what is known as "pH crash" - a sudden pH drop down to some very low number (3 or 2). This sudden change may cause death of fish and probably plants. However a pH crash seems to be more of a theoretical than an actual phenomenon - it seldom happens.
GH
Now GH of 17 is way out of whack. You will be better off bringing it down to more sensible levels - 3 to 6 is great, but even 9 would be ok.
I wonder how did you end up with such high GH. The first thing that comes to mind is that something in your tank (it maybe a single rock) is releasing Calcium in the water. But that would bring the KH and pH up too and that is not the case.
GH is a measure of the Calcium and Magnesium concentrations in your water. You can have GH =17 from Ca only or GH=17 from Mg only. Or mainly from one or the other. Without a Calcium test kit you have no way of knowing which one of the two elements contriubtes to such high GH. The Mg concentration is not checked with a test kit but it's calculated by using the GH and the Calcium - try this calculator.
If you don't want to get involved in testing Calcium and calculations you could try a simpler but very much blind approach. Test your tap water and if it has a GH considerably less than 17 then just do a few big (50% or so) water changes. That way your GH will go down but you will still not know the amount of Ca and Mg which are important for plant growth.
Another thing that may want to do is to make sure you check the pH more precisely. pH of "6 -7" does not mean much, usually you want to know if it's 6.1 or 6.9
--Nikolay
