[Vitellan]

Hi all
Long time browser
First post
I just set up a new tank with Flourite topped with Onyx sand.Tap water is 0kh and 0gh, filled the tank and kh is 2.5(I expected this) and the gh is 20 (not expected).
Is this normal when first set up?
Will the gh reduce over time?

 

[Rex Grigg]

Well first off welcome to the mess. There is no way those two substrates are not going to mix unless you never again touch the tank. The Onyx sand will end up on the bottom and the Flourite will end up on top. Simple physics at work there.

Since you did not give baseline figures for your water it's hard to say if the rise in hardness is normal or not. But Onyx sand will buffer the water.

 

[Vitellan]

Hi Rex
I know the Onyx will eventually mix in. I was originally planning to mix the Flourite and Onyx (because of the various nutrients in them) but decided to put the Onyx on top because I liked the look of it.

Concentration of nutrients in Flourite™………….Onyx Sand™
Aluminium……………………10210………………..822
Barium………………………...124………………….5
Calcium……………………….195………………….197500
Cobalt……………………….....6……………………4
Chromium……………………..13…………………..10
Copper…………………………17…………………..4
Iron……………………………18500………………..2846
Potassium……………………..2195…………………417
Magnesium……………………2281………………...115400
Manganese…………………… 64…………………...43
Sodium………………………..223…………………..135
Nickel…………………………12…………………...7
Vanadium……………………..15…………………...8
Zinc……………………………29…………….….…23

Flourite
Onyx Sand

My tap water is, KH 0, GH 0, PH over 8.8, after aeration with a 10cc springe for 30 seconds 6.4.
My parameters are now KH 4.5, GH 22, PH 6.4 (pressurised CO2) 1 day after a 30% water change.
Everything in the tank except the substrate was in the tank previously and I had to adjust the GH and KH up to 3 and 3. All the plants and fish seem to be doing fine.
According to the Seachem info only the pH (KH) should be increasing.

“but does have a slight buffering capacity that may raise pH by 0.1 - 0.5 pH units (depending on source water characteristics).”
Onyx Sand
Would the calcium and magnesium be dissolving into the water that fast?

Any ideas?