Hi all

Apologies for my first post being questions but I couldn't see an introductions section..?

I'm currently doing a fishless cycle for my new tropical tank and after making a mistake and using a non-API testing kit, I've just purchased an API master kit and also their GH & KH kits. Turns out I'm not as far along in the cycle as I thought I was but that's another story

My question relates to the GH/KH results - I'm absolutely sure I'm being a bit thick but the instructions don't make much sense to me. Would one of you nice people be kind enough to pass on some of your knowledge please.

Do I need to perform both tests on fresh tap water, 24 hour old tap water and tank water?

Also, how to I interpret the number of drops – the conversion table doesn't make it clear to me

Your thoughts and/or guidance would be very much appreciated!

Hi and welcome to FK,

Just test the tap water and the tank water. There's no need to retest the tap water for gH or kH after 24 hours as these two parameters won't change when water is left to stand - only pH does that.

To test kH, put 5 ml of tap or tank water into the test tube. Add 1 drop of kH test solution and shake. Repeat this until the solution changes colour from blue to yellow, counting the number of drops that takes and make a note of the number.

To test gH, follow exactly the same procedure using the gH test solution, but this time the colour will change from orange to green.

The numbers of drops equates to the number of German degrees of hardness in both cases. To convert either into ppm or mg/l, mutiply the number of drops by 17.9.

Hope that helps

Hi, thank you for the welcome and taking the time to post

It appeared too simple that one drop was equivalent to a unit of measurement but I suppose that's german efficiency in action!

Would you expect the tank and tap water to be different in terms of GH? The reason I ask is that the tank water took 16 drops to change and the tap water took 6. The KH for both tank and tap water was about 4 or 5 and the tank is mid fishless cycle, incase it makes any difference.

Thanks again and sorry for the basic/noob questions! I did try and use the search facility but didn't get very far - I suspect the user is the problem...

Sometimes the gH can rise in the tank due to minerals leeching out of rocks/gravel etc. What kind of gravel/rocks and decorations do you have in the tank?

Makes sense

Just a gravel substrate and a couple of rocks from the LFS at the moment.

I'm guessing the final big PWC when cycled will bring it down to near the tap water level. Is it then a case of doing further PWCs as the GH increases, until such time as it settles down (presumably it will..?)? Obviously I'll take all the other paramaters into consideration aswell.

Thanks again

It partly depends on the fish you intend to keep. Some have a wider acceptable range than others. It also depends to some extent on how fast gH is rising. How long has it taken so far to rise from 6 to 16?

The tank has had the same water (and substrate and rocks) in it for about 5 weeks, has been cycling for just over 4.

Do I need to worry about the increased gH affecting the cycle?

Thanks again, again!

I would think that with a couple of big water changes at the end of cycling and regular weekly changes after that you should be able to keep the gH fairly stable at a lower level.

It should have no effect on the cycle.