I am a strong believer in calcium reactors. I've tried kalkwasser, but for my tank I evaporate a little less than 30 liters per day, and keeping the calcium and alkalinity up meant more manual labor than I wanted. The two-part solutions are too expensive to do on this scale. I wrote an article on calcium reactors, and I plan to include it here soon.

I had a Knop-c calcium reactor on my 75 gallon tank, which worked well. There were some design flaws in the unit though; it would develop an air pocket at the pump intake and eventually flow would stop. Worse, the air pocket is trapped under the media, so it is a real pain to get it out of there! Still, the unit worked much better for me than kalkwasser or two-part solutions.

I unfortunately broke the unit when moving (as you see in the picture). I traded the unit to someone for credit at a local store.

When I built this new tank, I wanted to build my own reactor, since they are fairly simple devices that cost a large amount of money. Sadly, the pressures of building a new house prevailed, and I ended up having to buy one. I chose a Korallin reactor. It is really well designed and well built - superior to the Knop. It's only problem is that it is a bit of a pain to refill since you load it at the top, but you only refill every 6 months, so not a huge deal.

I upgraded to a 20-pound CO₂ tank since I have the equipment room to hide it in. One tank of CO₂ lasts me about a year - I am using about one bubble per second. 

Some thoughts on media

I've used Koralith media with great success. This is the media I would recommend to anyone. More on that down below.

I tried super-calc gold (lower price) which I find doesn't dissolve as readily, probably because of less surface area. You see in the picture at right that the top 1/3 is Super Calc, and the bottom 2/3 is the Koralith media, so you can see the size of the grains is much different. Koralith is about the size of the larger grains of Caribsea Reef Sand, while Super Calc Gold was about pea-sized grains. Also, the Super Calc has lots of dark spots, orange and black embedded in the grains. This is clearly impurities of some type. I don't know what it is, and maybe it isn't going to hurt anything, but it makes me nervous to have mysterious dark stuff embedded in the calcium carbonate! Initially, the SuperCalc seemed to work fine. After about a month, the reactor effluent with SuperCalc was only about 14 dKH, even though the pH was 6.5. This is clearly not going to do the job. With the Koralith, the effluent stays around 35 dKH, even after a couple months.

I also tried the new CaribSea ARM. This media has some nice features - it dissolves significantly more easily than any other media I've tried. Even with the pH around 6.9, the effluent stayed at around 40 dKH. It is also about half the price of the Koralith. The grains look like the larger grains of Caribsea reef sand, or perhaps a bit larger. Unfortunately, this media has a big downside as well. After using it about a month, I started getting increased algae growth. After two months, the trend hadn't reversed, despite my adding additional snails/crabs. Finally, I started to get a hair-algae outbreak.  Since nothing else had changed, I switched back to Koralith media. Sure enough, since then the algae growth has stopped and the algae is nearly gone again. My theory is that the large amounts of dissolved media released enough phosphate to let the algae take off. I couldn't measure any phosphate, but it was obviously there since algae requires it to grow. As I pointed out elsewhere on this site, my experience is that if phosphate is the limiting factor for your algae, the algae will use up phosphate so readily that you will never measure any in the system, though it is obviously there (since the algae grew!). If your system is limited in some other respect (light, nitrate, something else) than you may be able to accumulate phosphate to measureable levels. In both my reef tanks I have never, ever, measured phosphate using the low-range Lamotte kits. I find it is almost always the case in a reef tank that phosphate is the limiting factor for algae. It certainly won't be light, and nitrates are always present from animals in sufficient quantity to grow algae. Note that I can measure zero  That is certainly true in my tanks.

The Koralith has more consistently sized grains than other media. It performs well over the long haul, and doesn't cause any algae outbreak. 

With the reactor going 24x7, my pH ranges from 8.2 to 8.3 during the course of the day. This is a bit odd; since for the first year my pH ranged from 8.0 to 8.2. I use a simple Pinpoint pH monitor. I actually have a pH controller that I bought with my first reactor, but I found that I never use it. My reactor runs all the time anyway. My effluent drips back into the sump from several inches above the water level. It drips right above the intake to my ETSS skimmer. This assures that even if my CO₂ regulator goes crazy and I blast CO₂ into the reactor, the excess CO₂ will blow out into the room, not bubble under the water. And, the effluent gets sucked into the skimmer and quickly the CO₂ levels are back to equilibrium. This ensures that I don't fill my tank with CO₂ and kill everything. The water from the reactor is saturated with CO₂ anyway, so the water going into the sump can't possibly carry more CO₂ than it does. The only remaining danger is that the effluent drip rate would suddenly get very high, driving the pH down too low, but I cannot imagine how this could occur accidentally. Someone would have to turn the mechanical valve, which really isn't under pressure anyway, so pressure couldn't blow it out. Anyway, I think I'm safe without the pH controller on the CO₂ tank, and I wish I hadn't spent the money.

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Last modified: January 29, 2002