Just to chime in with some personal experience with peristaltic pumps in general and those from
www.reefdosing pumps.com in particular. I bought the low end item from them a few years ago. These are rebuilt medical dosing pumps and are designed to pump relatively low volumes of liquid. I ended up running towards the high-end of the specified volume and ran into several problems.
First of all, the tubing connections they supplied with my particular pump were not even hose barbs. They were just simple tubing slip fittings. So, if there is any back-pressure on the dosing pump (like from that Nilsen reactor you're talking about) the tubing will slip off rather easily. I discovered this the hard way: water on floor, with kalk dripping backwards from the reactor onto the floor also. Luckily this is in the garage!
The second part is that these are designed to be used in hospitals and have many parts that fail easily in corrosive environments. So far I have had a float switch corrode as well as the metal grommet around the float switch plug on the pump itself. The float switch was replaced immediately (I have rarely experienced such great customer service as from the guy that makes these.) The corrosion on the grommet has resulted in an intermittent partial short across the float sensor input wiring, which basically bypassesthe sensor for some or all of the time, depending on how much voltage is going across the input. I'm guessing this is a 12V relay for the float switch so when the circuit is connected it de-energizes the main pump. Pain in the kiester. If you do go with one of these, make sure to mount it WELL away from your set-up.
The last problem was the rather sizeable straw on the camel's back. (not that I have a hump-back, excessive hair, cloven hooves, smell funny, spit excessively, or in any other way resemble a camel....) As mentioned earlier, I was using the pump pretty much continuously and had to use several tweaks to get this thing to actually push out near the specified maximum flow rate. After a few weeks, the tubing split. Not a big deal, I've used professional peristaltics in pharmaceutical manufacturing plants. Tubing splits occasionally. So, I cut it out and replaced it. It split again two weeks later, and again a week later, then a few weeks later. I ordered more tubing. It kept splitting. So, I figured that I was just pumping too often, so I went and bought larger bore tubing (pumps more liquid so fewer pump revolutions are needed.) This split. So, I spent some quality time looking at the pump mechanism. On this particular model there is a rather sharp lip on the peristaltic wheel. Even after filing it down it still split the tubing.
I saved the pump for a time when I can rebuild it, and use it to slowing drip water into a
quarantine tank for automatic acclimation of new fish. However, I bought a reef-filler pump. It can handle quite a bit of back pressure (great for mounting in remote locations and pumping through a Nilsen reactor.) It is moderately loud, which I knew when I bought it. It can be purchased with a fairly large pumping range. I bought one of the higher-range pumps for use on the dream large system that I plan on setting up in a few years. It is nice to be only using 5-8% of the pumping capacity. As for the litermeters, I have also heard great things about them. They have a tremendous feature set with a built in computer which can also control two additional slave pumps for automatic water changes or intermittent 2-part solution additions, etc. For my purposes, however, I did not need the additional feature set and simply wanted a reliable high power dosing pump which was designed for industrial corrosive applications.
As for the noise, I find it to be about 1/2 as loud as an unmuffled stand-pipe. I can't hear it above the other tank noises. However, as mentioned earlier, this system is in my garage and has absolutely no effort put into quieting down ANYTHING. This is a loud system, so one more loud part is no big deal. I have seen rather nice implementations with a Nilsen reactor where a large RO/DI bucket, the pump, and the Nilsen reactor are all mounted in a remote location (a closet, the basement, the garage) and only the small tube coming from the Nilsen comes into the house. This takes care of the noise, as well as any potential spills of very corrosive
Calcium Hydroxide solution or poweder in the house whenever you top off the Nilsen.
Best of luck, and with either the litermeter or the reef-filler I'm sure you'll be happy.
Josh Fox
P.S. I guess you can add this to the list of really good reasons to buy the best you can afford the FIRST time!
