Kalkwasser

kharn101 · Mar 20, 2026

Hello All,

I’ve decided to set up a still kalkwasser reservoir to help address my low pH.

For equipment, I plan to use the following:

FX-STP2 continuous pump to dose kalk at a controlled rate
5-gallon BPA-free container with cap
Amazon product

I see the pump uses 1/8-inch tubing. Should I use silicone tubing or polyurethane tubing to connect it?

I’m also trying to visualize the full setup, including installing a bulkhead union. Most options I’m finding are 1/4-inch, which seems larger than what I need for the container.

My understanding is that I would drill a hole in the container, install a bulkhead, and run rigid tubing inside so it sits above the kalk slury,

Could someone walk me through the full setup, including:

Bulkhead sizing and recommendations
Transition from bulkhead to push-connect fittings
Proper tubing type and sizing
What tubing should feed into the FX-STP2
What rigid tubing i should use to hookup to the bulkhead?

Appreciate any guidance on how to properly configure this.

mcarroll · Mar 25, 2026

If your tank is having a problem other than the pH number I would ID that first.

Then if there was still a situation with pH after identifying the problem, I would validate the pH reading somehow (eg. Randy's pH test) and then if a problem was indicated, I would get more air to the room, or whatever solution the test indicated. (In a lot of cases, the sump just needs more ventilation, or the fish room itself just needs to have the door left open maybe with a fan running. Only a few cases I'm aware of where someone had to make a change to their HVAC to solve the issue. (Most folks don't really have a pH issue tho....they just see a pH number on a test that a website says is "low" and then start looking for a problem. That's classic "pH chasing".)

Using kalk for pH boost sorta counts as chasing pH in my book because the effect is so limited in time frame.....the great aeration we provide in our tanks will re-saturate the water with CO2 in very short order bringing pH back down. I don't see why this is much better than using pH Up, which nobody uses.

Now, if you want to use kalkwasser anyway just because this is how you want to dose calcium and alkalinity, then that's a different story. Go for it! :D

If you haven't yet read Randy's experiences using kalkwasser on his old tank, I would strongly recommend reading about his setup....and emulate it to the extent you're able to.