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Nilsen Reactor

There are several designs for Nilsen reactors, the most cited seems to be those by Fabrice POIRAUD-LAMBERT and those modified by Bill Esposito. They use a small powerhead to mix the kalkwasser in the reactor. Kay Wilson also has put together quite a detailed description of her version of a Nilsen reactor that she sells. She uses an external stirring motor with only the stirring bar in the reactor and in contact with the concentrated calcium hydroxide solution. Refer to the the page by Fabrice for information on the chemistry.

I decided to follow Kay's design and use a stirring bar/motor to mix the kalkwasser. I use my LiterMeter dosing pump to pump fresh water into the bottom of the reactor to mix with the concentrated kalkwasser and the clear kalkwasser exits the top of the reactor. Fresh kalkwasser is made four times a day when the stirrer is activated by a digital timer for two minutes. The solution quickly settles with maybe only one dose of the milky kalk getting into my sump per cycle. The reactor is sealed to prevent the reaction of the calcium hydroxide with air, reducing the effectiveness of the kalkwasser solution.

Item Source Cost
Toilet supply tube Lowes (building supply)
$20
Flat 4" PVC cap Local farm supply
4" x 2" reducer Lowes (building supply)
2"x1.5" reducer Lowes (building supply)
1.5" male thread Lowes (building supply)
1.5" threaded cap Lowes (building supply)
1/4" plastic tubing Lowes (building supply)
4.5" clear acrylic tubing Aquatic Ecosystems
$18
4" diameter x 1/4" thick glass plate Local glass shop
$5
LiterMeter dosing pump
$250
stirrer motor and stir bar Hanna HI 190M (later replaced with a used Fischer Scientific Accumet Stir Plate which is a lot stronger and far superior)
$66

($19 off eBay)

Digital Timer see below
$13-$70
Calcium hydroxide, Mrs. Wages pickling lime Local grocery store
$1.29

I used a flat 4" cap for the bottom so the reactor would sit on the stirrer motor. The round glass plate is placed on the bottom of the reactor before the top is sealed on. This glass plate eliminates wear on the plastic bottom cap from action of the stirrer bar combined with the calcium hydroxide (thanks, Kay!). I permanently cemented on the bottom cap using PVC cement but used silicone glue for the top (reducer) so I can take the top off if I ever need to. The threaded 1.5" cap makes it easy to add kalkwasser powder. I could have used a plug but thought it would be hard to open with me bent over. I have the fresh water enter at the bottom vial the toilet supply tube which mixes up a small amount of fresh kalkwasser every time the dosing pump activates.

I already had the dosing pump for my make-up water so I figure it only cost me about $210 for the reactor. That is a far cry from $650 for a calcium reactor.

I have gone through several iterations of strirring my reactor. Here are my experiences with various controllers:

Timer
Cost
Pros
Cons
Radio Shack 4 event timer
$25
Reliable, inexpensive Only 2 stirrings per day - did not meet my calcium and alkalinity needs. This is the one I am using today.
X-10 Appliance Module
$13
Cheap Requires an X-10 controller and is as reliable as your X-10 system. Mine was reliable enouh but I had to program 12 on and 12 off events run stir the reactor every 2 hours. It was a pain to change.
Timer, recycle, Amperite 120AF/FDFA
Adjustable1-100 min on and off cycles.
$70
Easily adjuistable. Not cheap, requires wiring into a electrical box.

The solution in the reactor gets thick and cloudy when stirred but settles quickly. I typically measured Ca at 700-800ppm and alkalinity at 30 meg/ml at the reactor outlet. This compares well with a Calcium Reactor but is a lot cheaper and less hassle. I'll let you read what Craig Bingman has to say about the other advantages of kalkwasser. The reasons I prefer dosing kalkwasser include:

My tank has never looked better. The back glass is now covered with coralline algae - something I could never get with dosing B-ionic (lots of it, too.) My corals, including acropora, are also growing well.

updated 12/11/2006