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Is my gravel raising pH, KH and GH!

3516 Views 3 Replies 3 Participants Last post by  pauliosa
I am using a course (10-20mm), slatey/quartzy type gravel as cap. My pH, KH and GH levels are elevated from those of my tap despite 15-20 % of my tank volume being driftwood leaching visible tanins. I steeped some gravel in tap water for 3 days and this gave also elevated levels, although not quite so far.

All stone has been bought from an aquarium store.

Tap is 6-6.5 pH, tank is >7.5.

I cannot find any info on why this may be happening online so any ideas guys.
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You already answered your own question... the gravel is changing your parameters. You have 2 options. If it is a problem then you can replace it with an inert substrate. If it is not a problem then just let it hit its equalibrium and leave it be. Lots of substrates buffer the water. It is common.
One more option is to treat the gravel as if you were dosing something to raise the calcium and magnesium in the water. You would be dosing too much, so you just do 50% water change weekly or every other week, and that drops the GH, etc. enough so it doesn't get too high. If you wait too long before doing that water change it may cause a too big change and bother the fish, but weekly or every two weeks should work out well.
Thanks guys,

So I have tested some crushed up slate/quartz substrate and pH >8 so am pretty sure this is the cause.

I have no more than a big handful of the stuff in my tank and most of that has only been in a couple of weeks but is enough to take me from below neutral to being over. I think it would need to be weekly 50% to retain soft water.

I will probably remove it but has certainly opened my eyes that substrates in the trade will do this, even when not stated.
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