Media Reactor for Kalk


New member
I've had no luck keeping SPS coral and suspect the problem is alk stability. I dose kalkwasser with top-off and supplement with two-part (anhydrous baking soda and Seachem Reef Advantage Calcium - hard to get dow flakes in San Diego). I really struggle to keep alkalinity and calcium stable. Alk fluctuates between 8 and 10 dKH over the course of weeks. Other parameters are relatively stable so I'm pretty sure this is the problem.

Latest tests:
Alk: 8.0 (deliberately brought down from 10 over a 5 week period but there were a couple 1 dKH swings)
Ca: 420 ppm (more stable than Alk but still not very stable)
Mg:1290 ppm
NO3 0.2 ppm
PO4 0.02 ppm

I like Kalk because it's a balanced Alk and Ca, helps with low pH (I know, not a big deal but my tank runs between 7.9 and 8.1 with kalk), and Mrs. Wages is very inexpensive. I think my problem is consistency of dosing with top-off since evaporation is not always the same. The result is I'm constantly tweaking the 2 part to compensate. Another problem is that I am picking up some of the supersaturated water near the bottom of the ATO reservoir, which I've read is bad.

Proposed solution: I have a large media reactor that I currently use for GFO. I'm thinking of using something else for GFO and instead pouring a bag of Mrs. Wages into the reactor and filling it with RODI so it's saturated on top with the remainder sitting on the bottom. Then I'll use a BRS dosing pump to push RODI water from my topoff container bottom up through the media reactor, which would then drip into the sump from the top at the notional rate of 1.1 ml/minute.

Meanwhile, the auto top-off would continue to take care of evaporation with RODI water from the ATO reservoir.

- Any issues with the Mrs. Wages clumping on the bottom or will it dissolve and keep the kalk saturated as new water enters the reactor at a rate of 1.1 ml/minute? I've seen kalk stirrers but is that really necessary or will the slow flow of water be enough?
- I'm using about 1 - 1.25 gal/day in top-off. I know the BRS doser can't move that much water so I'll still have to use 2 part. It just seems to me that I would be able to dial it in better if I could keep kalk coming in at a constant rate independent of evaporation. Anyone see problems here?


New member
The Mrs Wages ( or any kalk powder) will clump if there is not enough disturbance. I use a standard 10" water filter housing plumbed in reverse, which works as a great little kalk reactor- do a google search for DIY kalk reactors & you'll get a good idea how they work. All my top off (approx. 2 gallons daily) is replaced by kalk via a Tunze Osmolator feeding into it. I would consider using kalk to replace all your top off if possible. I empty the reactor every 2 weeks & dump the crud out & replace with 2 cups of fresh powder- only takes a couple of minutes & ensures the kalk is full strength. A pH test would also show when the kalk is dropping off in saturation. HTH some