Kalk (Nilsen) Reactor DIY

This DIY Kalk Reactor is designed to allow easy Kalkwasser (Calcium Hydroxide, Pickling lime) to a reef aquarium. My reactor is designed for low and easy maintenance and easy setup. If you can’t tell from my other DIY ideas. Cost is one of the biggest driving factors for me. So of course this is very cheap to make.

• 1/2″ Electrical PVC adapter MPT X 3
• 1/2″ Electrical PVC adapter FPT X 1
• 1/2″ PVC FPT – Slip elbow,
• 1/2″ PVC FPT – FPT Adapter,
• 1/2″ PVC FPT – Slip Adapter,
• 1/2″ PVC slip – Slip Elbow x 2
• 1/2″ PVC slip – Slip Coupler
• 1/2″ PVC FPT – Slip 45,
• 1/2″ PVC Schedule 40 pipe,
• 1/2″ Rubber o-ring (11/16 I.D, 15/16 O.D, 1/8″ wall)
• Rubbermaid 1.3 Gallon food container
• Powerhead (Maxi-Jet 400)
• Zip Ties
• Drill
• Hole Saw 3/4” (Harbor freight is where I got mine)
• Sand paper
• Epoxy

1. Start off by marking where you want your holes to be. I actually wish that I put all the holes on once side.
2. Place the drain about 1/2 inch lower than the inlet. Place the cord hole as high as possible. It will be water tight, but if it’s not submerged then leaking is even less likely.
3. Using a 3/4″ hole saw, drill the marked holes. This plastic is the easiest hole to drill. I’ve drilled several plastics and the polypropelene of this container goes smoothly without any problems. Go slow and don’t press hard. Sand the edges of each hold to remove burrs and any remaining lip.
4. Using the 1/2″ electrical PVC and the washers make bulkheads for each hole. The electrical PVC fittings are different from the normal white fittings in that the threads on the male pipe fittings do not taper, allowing you to tighten it all the way down to the o-ring. Conventional PVC pipe fittings will not allow such a snug fit.
5. Here’s a little detail on the mixing pump setup. I attached the mixing pump to the drain input since it would center the pump in the container. This allows for optimal mixing of the kalkwasser with any new water that has come in. You’ll need to drill a small hole at the top of the outside elbow as a siphon break. This will help ensure that it drip drains.
6. After getting the pump installed it’s time to feed the cord. When I designed this, I wanted to make sure that it was easy to open and add more kalkwasser whenever I felt like it. That meant no holes in the lid. The lid has to stay on so that the air is sealed. The lid should befreely removable, but securely installed. This means the cord has to go somewhere else. This is the purpose of the last hole. Cut the cord near the plug so you have lots of cord left to reach a receptacle.
7. Thread the cut end throught the last bulkhead. Fill the hole with epoxy to make it water (and air) tight.
8. Add a plug end on the end of the mix pump cord that you cut on earlier. Plug it into the mixing timer.

Fill the reactor with RO water. Add a a cup or so of kalk powder to the reactor. The reactors job is to generate saturated kalkwasser solution for dosing. The water and kalk powder are mixed and the kalk powder dissolves into solution with the water. As long as you keep adding enough kalk powder to the reactor so that there is always some undissolved powder settled on the bottom you will have a saturated solution of kalkwasser ready for dosing.

When dosing is desired, pump water into the reactor using an external pump or pressurized source, usually a med dosing pump or an aqualifter pump sometimes a ro/di filter outlet. The purpose of the special pump is to slowly add RO water to the reactor inlet. Saturated water from the bottom of the reactor seeps up the drain tube and out into the aquarium. The water level in the reactor always remains constant. Fresh water comes in and kalkwasser goes out.

The mixing pump mixes the new water and the kalk powder residue sitting on the bottom of the reactor. Time the mixings such that dosings occur after the kalk has settled so that you don’t dose the aquarium with straight powder. The kalkwasser reactor can hold quite a bit of kalk powder. After new water comes in and kalk solution goes out, the new water is made into Kalkwasser in the mixing process. Air interaction with the Kalkwasser mix will cause some kalk to precipitate to calcium carbonate. Keep the lid on to minimize this reaction. Calcium carbonate is harmless it just wastes the kalkwasser. If fact, aragonite sand is made of calcium carbonate.

I have the dosing timer set to just be under normall daily evaporation requirements. I set the timer to pump for 15mins at a time evenly dispersed throughout the day. For the mix timer. I first synchronize the two timers (I use the same brand for both) I pick two times, both right after a dosing interval to mix. Make sure there will be at least 1 hour of settling period before the next dosing on the dosing timer.