My Kh Conundrum?

Tap <1 KH, <1 GH, 7.4 PH.

I've been dosing an Alkaline Buffer twice a week and achieved 3 KH, doesn't seem to want to go higher.

I'm using a GH Buffer and achieved 6 GH - I'm happy with that.

My PH has been very stable at 7.4 PH the whole time. I'm really not concerned about PH swings as I've not had any.

I do weekly water changes of 50+ %, and my PH stays at 7.4 PH.

So why do I want to increase my KH?

I'm under the impression that 5 KH would be healthier for both fish and plants. Am I wrong?

I've been advised to double up on my Alkaline Buffer dosing from 45ml twice a week, to 90ml twice a week. But at that point I'd be spending more money than I care to on the buffer.

So I'm planning to add Crushed Coral.

With no room left in my filter I will load some crushed coral into a couple of filter media bags and bury them under the substrate (lava rock gravel).

But here's the conundrum - if my PH never falls below 7.4 PH, I'm guessing my tank water won't be acidic enough to erode the coral, and therefore the coral will not increase my KH.

Is this right?

I really only want a stable 5 KH.

 

It won’t erode under the substrate. It needs water moving through it so really needs to be in a filter.

KH is required to prevent pH crashes. Whether the fish and plants need it depends on what fish and plants they are.

 

It won’t erode under the substrate. It needs water moving through it so really needs to be in a filter.

KH is required to prevent pH crashes. Whether the fish and plants need it depends on what fish and plants they are.

Thanks Coptapia - my little Fluval C4 filter is simply full of media. No room left in there, and I can't bring myself to remove media that has established benificial bacteria.

I had heard that you can mix the crushed coral into your substrate, but you'd need more of it to have the same effect as a small amount in the filter?

I was planning the buried media bags to hide the coral and make it easy to take out or replace.

But you've provided another reason my plans won't work.

P.S: Fish = 2x Pearl Gourami. 16x Red Eye Tetra. (plan to add 4x German Blue Ram and 2x Apistogramma Cacatoides Orange Flash).

Plants = Italian Val. Indian Sword. Limnophilia Sessiliflora. Egregia Densa. (plan to add banana plant, Dwarf Lily. Tiwian).

 

It will dissolve more if mixed with the substrate, because some will be on top. Personally I would rather use a tiny amount of MalawI Salts, which is a lot easier and more accurate. Crushed coral dissolves very slowly.

None of your fish need much KH. I don’t know about the plants.

 

As long as you are willing to monitor your KH and pH a 3dKH is perfectly fine. It's kind of the bare minimum recommended to keep pH from suddenly crashing.

Plants use KH as a source of carbon, especially if another source of carbon isn't being supplied. So, if your plants use your supply of KH, that leaves your pH vulnerable to a crash. I think people are picking the 5dKH purely for their comfort level because it buys them a little more time and don't have to watch the KH and pH maybe as closely. So, the answer to this riddle is... it depends on what your plants are using for a source of carbon and how quickly.

Any time you alter KH, pH is likely going to be affected as well. So increasing the KH may very well and is likely to increase the pH.

Aragonite (a type of substrate often used in cichlid tanks), will also increase your KH quicker I believe than crushed coral, but it too will increase the pH. Probably a couple of tablespoons in a media bag in the filter is all you'd need, adding more if required.