[neon20L]

I was setting up a new tank and after adding Caribsea Flora Max substrate, my pH went from about 7.5 to 8.2-8.4. My tap water is 7.5. I've done a couple water changes and within 24 hours the pH is back at 8.2-8.4. Obviously the issue is with the substrate, but I'm not sure how to correct the issue.

I suppose one option would be to replace the substrate with something else. Another option would be to reduce the pH somehow, but I'm not sure if adding pH down will actually fix the issue, just be a short term fix, or cause other problems. I want stability, not having to constantly monitor and tweak the pH due to the effect of the substrate.

Any ideas? Thanks

(just to be clear...there are no fish or plants in the tank yet and won't be until this is resolved)

 

[WaterLife]

I've never looked into FloraMax, but just saw a image of the bag, and it says "Will Not Raise pH".
So, double check if it really is the substrate raising the pH.

Maybe it's just your tap water has quite a bit of dissolved co2 causing the pH to be 7.5, but after degassing most of the dissolved co2, it would be 8.2? Seems pretty drastic though.

If it really is the substrate, see if it contains carbonate or bicarbonate sources (which would raise KH), such as Calcium Carbonate (crushed corals, oyster shells, eggshells, aragonite, etc).

If it is the substrate raising the pH, it would be pretty hard to combat the alkalinity buffering. Would be less hassle/much easier to use a different substrate (inert).

 

[neon20L]

Interestingly they covered that statement on the bag w/ a sticker that says "may raise pH". I figured I'd give it a shot and maybe have no issues, but guess not. Just pulled it out of the tank and will go get something else.

 

[WaterLife]

Ohh, the picture I saw on some website showed the bag saying "Will Not Raise pH". Guess they changed that

If you wanted to, you could do some google searches on "Caribsea Floramax raise pH" or something along those lines, to see if anyone else had issues. Though the new statement on the bag may mean they have changed their "formula" and now it may contain something that would raise pH.

Still worth reading over the ingredients list on the bag if there is one.

 

[Nlewis]

Leave some of your tap water out for about in hour and test it. Like Water said you may have some co2 in the tap that's dropping the ph. In my case my water from the tap test out at 6.2, but degased tap water test out at 7.6.

 

[Diana]

Set up some jars of water: Test GH, KH, pH, TDS.
1) has just tap water. Let it sit out 24-48 hours and test.
2)...3)... etchas tap water with whatever additives you use (one jar per additive) to prep the water for the tank.
4) has a handful or two of substrate and tap water. You could test within an hour or two, then test the next day, and perhaps one more day later.
5)... 6)... etc. have other things from the tank, one item per jar of tap water. A stone, a chunk of driftwood, whatever is in the tank.

This way you are testing everything in the the tank separately to see if it might be something other than the substrate.
Things that usually raise the pH also may raise the GH, KH and TDS. Limestone sand and rocks, shells, coral and similar things commonly do this.

 

[neon20L]

Turns out it is the water, not the substrate. I got impatient and changed out the substrate to an inert gravel and same issue 24 hours later. So now I'll probably switch it back to the Flora Max.

The area I live in has very high GH (lots of calcium and limestone). I do own a RO/DI filter (for the saltwater tank), so could just use water from that.

 

[Diana]

GH does not affect the pH. GH is a measure of calcium and magnesium.

What is the KH of your tap water? KH is a measure of how the water resists change in pH. In aquariums this is usually carbonates and bicarbonates. (KH translates as carbonate hardness).
High KH almost always means high pH, and hard to change the pH.
Low KH usually means something else in the water will control the pH. Usually the pH will be easier to change.

A blend of tap + RO might be a good answer.

Run some tests, various ratios of RO:tap and see how they behave over a few days.