My GH and kH keep increasing

What kind of substrate and rocks do you have?

 

I'm not really up on this stuff...but isn't flourite a substrate?

KH=carbonates
GH=calcium and/or magnesium

There are only three options -
1. something in your tank is leaching them (most likely - corals, shells, rocks possible culprits)
2. you are adding them (don't know what seachem flourite is, but otherwise nothing you are adding will increase these)
3. you are topping off evaporated water with tap water during the week

If you think something is leaching them, take it out and rinse it off well, put it in a bucket with distilled water. Test GH and KH the next day or a couple days later. If any readings show up, you've got your mystery solved.

 

It is. He probably meant Seachem Flourish.

 

Is this the aquaclay you use: Aquaclay - Ground substrate It appears to be a baked clay product similar to Soilmaster or Flourite. But, I don't know what is in it or if it is intended to buffer the water. It's primary usage seems to be as biological filter media.

 

Distilled water should have extremely low GH and KH, zero in theory, but probably not in ordinarily available distilled water.

 

I think that you have found what the problem is. If you can get a l degree rise in both KH and GH in one week, the aquaclay probably contains calcium carbonate, and some of that is leaching into the water. If you had more surface area of the aquaclay vs the water volume it could have gone much higher. When we use a material for a substrate that wasn't designed for that use we always have some possibility that we will affect the water in some way. The same is true when we add a rock or piece of wood to the water. If you do regular water changes you can reduce that effect to where you don't need to worry about it.

I'm currently testing a rock in a similar way to what you used, but I'm using about a quart of distilled water because of the size of the rock. After a week I will see if my distilled water has any GH or KH. When doing this it is important to avoid any evaporation of the water or the GH and KH will go up just from that. Mine is sealed with plastic wrap to avoid that.