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Dosing Station

Project: Implementing A Supplement Station

Keeping a successful reef tank is all about maintaining stable water parameters. Water temperature and specific gravity aside, foremost in this effort is the maintenance of correct levels of alkalinity, calcium, and magnesium, all three very important to the success of a reef system - especially if SPS corals are being kept.

One often utilized means of maintaining these levels (at least as far as calcium and alkalinity are concerned - although, with the use of minerals like dolomite, magnesium can also be dosed) is the use of a calcium reactor. My past experience with Ca reactors has taught me that they have at least one negative aspect - because CO2 is required in their application, the reactor's effluent has a pH value that is much lower than desired. This, over time, causes problems maintaining the system's pH at an acceptable/desired level.

Another, and to my mind, more elegant way to achieve the desired Ca, Alk, and Mg, levels is through direct chemical dosing. An automated dosing station gives relatively simple control of the supplements being added to the system, and allows for minute adjustments, when required.

The addition of liquid supplements to the system is best done with peristaltic (also known as dosing) pumps. There are dosing units on the market made specifically for reef systems. They can be had in 2, 3 and 4 pump versions. They work very well, but have a very high purchase price. Being the frugal person that I am, I decided on a standalone pump sold by Bulk Reef Supply (BRS): 

Known as "Drew's Pump", it moves 1.6ml of fluid per minute. This makes it perfect for supplement dosing.  Based on my mixing formulas (I like to use a starting dose of .3 to .4 ml per gallon for each supplement), my system needs approx. 130mL a day of each supplement (Alk, Ca, Mg), so three pumps would be required.

I needed a way of turning the pumps on and off a number of times each day and making sure the on times were exactly regulated. Electronic timers were the obvious solution. I had experience with timers from Woods and found them to be extremely easy to use and very reliable. They provide up to eight ON-OFF cycles per 24 hours and most importantly, in our wet environments, 3-prong (grounded) sockets:

So, I built three compact "dosing stations", each comprised of an electrical outlet box, an electronic timer, and one of the Drew's peristaltic pumps:

Together, the three stations pull the supplements from 2-1/2gal flasks located below each station:

The supplement flasks were obtained from Bulk Reef Supply. I drilled a hole in the cap of each flask and attached a Jaco fitting to tightly hold 1/4" RO (PE) tubing. I also drilled a 1/16" vent hole in each cap, to relieve pressure as fluid is drawn from the flask.

As I mentioned, my system needs approx. 130mL of each supplement. I decided to take full advantage of the timers' 8 cycles-per-day capability. It's not a good idea to dose the supplements simultaneously (especially Ca and Alk) due to the probability of precipitation, so I set the timers up in a staggered fashion. Each supplement is set up to be dosed 8 times a day. Each ON period is set for 10 minutes. That makes 80 minutes X 1.6mL = 128mL - very close to the 130mL I was shooting for.

Dosing times:

  • Alk is dosed at 12:00, 03:00, 06:00, 09:00 - both A.M. and P.M.

  • Ca is dosed at 01:00, 0400, 07:00, 10:00 - both A.M. and P.M.

  • Mg is dosed at 02:00, 05:00, 08:00, 11:00 - both A.M. and P.M.

You can see that the doses are staggered one hour apart so that  no two supplements are dosed at one time.

All in all, I have found this setup to be very practical. It is amazing how stable the system's parameters are. I have the Alk stuck to 8.3, the Ca at 440, and Mg at 1350. The supplement jugs only need to be refilled once every two months. Beats the heck out of using a Ca-reactor!

Oh, almost forgot - the supplements are pumped through normal 1/4" RO tubing (PE). The three lines are color coded and are enclosed in a 3/4" PVC pipe that runs along three walls of the fish room - from the dosing station to the sump:

I needed a way to mount the tubing in the sump, but I didn't want to make it permanent, so I came up with some tubing holders (clamps) using Jaco connectors. The clamps serve to hold the tubing to the sump's Euro-bracing without having to drill holes. I decided I needed a triple holder for the supplements (Alk, Ca, Mg) and, as using the same type of holders for the automated water change function seemed like a good idea, I made two single holders, also - one for old saltwater removal and one for new water in.

I made the clamps out of 3/8" acrylic sheet, 1/4" Jaco fittings, and 1/4"-20 nylon thumbscrews:

I drilled out the Jaco fittings so that the 1/4" tubing will pass completely through the fitting. That allows the tubing to go all the way down into the sump. The clamps are held onto the sump's Euro-bracing by tightening the thumbscrew(s).

Here's a single clamp:

And here's the triple clamp for the additives:

In the next pic, you'll notice that the ends of the supplement tubing lines are submerged below the waterline in the sump. This is not a good practice as some supplements, especially Alk, tend to clump and solidify where they exit the tubing if the ends are under water. Always leave the tube ends at least an inch above the surface of the water. This picture was taken the day the sump and it's components were completed - unfortunatley before the final adjustments were made. My thanks to Nick (see comment section, below) for noting the error.

You may have noticed that I didn't take the trouble to polish the edges of the acrylic. My a-retentiveness does have it's limits.

This is how they look installed:

BTW: the 6" acrylic tube sitting in the sump is used to stop any wave motion around the ATO float valves. There are two 3/8" holes drilled at the bottom of the tube to allow the water level in the tube to rise and fall. Works real well. The ATO has only 1/8" difference between "full & fill".

Here's a close-up of the connectors in place:



Adrian Barrett says...
Great site to hop onto and read. I come here from time to time just to check out the fish room and DIY tutorials. Recently had problems with alk and got the 2 dosers from BRS but the 1.1ml per minute ones... apparently I have to dose about 100ml per day on my total water volume of 146 gallons... how come you were only dosing 130ish for your size tank?


29th May 2012 9:42pm
Kevin says...
I have enjoyed wandering through your site, lots of great ideas (like a dosing station!) I was wondering how long you have had the Woods digital timers in service and how reliable are in your experience for this application. Reviews at Amazon are split, just curious if they've been good, bad or mixed for you.
GlassReef: Glad to hear you like the site! The Woods timers have been in service since February 2009, so almost two years. I do have a check list hanging on the wall of the fish room that I go through twice a day. One of the things on the list is the dosing station. I make sure that all is in order, including the timers. I don't check them because they normally have problems, they don't. I check all components of the system where a failure could cause serious problems. It goes without saying that a serious system failure, especially in a system as large as the Glass Reef, is to be avoided, if at all possible.
11th January 2011 4:10pm
nick says...
have you encountered any problems with having the tips of the supplement lines in the water or is that done on purpose to prevent crust from forming and blocking off the flow??
GlassReef: Good catch, Nick. I didn't notice the pic with the tubes in the water until I read your comment - and you're absolutely correct - if the tubing is underwater you can have trouble with the Alk caking solid at the nd of the tube. It can get so bad that the flow is cut off completely.

My only excuse is the pic was taken when the sump, etc. was first being set up. Unsure I'll insert a note about the situation in the existing text. Thanks for the heads up!

22nd October 2010 12:19am
Brian says...
I must say, you have a talent for packing your articles with information! I haven't yet moved away from my trusty calcium reactor, but I'm thinking seriously of doing so. There are companies that say that the chemicals being sold by bulk distributors are not pure enough for our reef tanks. I have to admit I worry about this kind of thing. Any thoughts?
GlassReef: Well, Brian, I think in almost all cases the warnings are much ado about nothing. Also, I think you'll find that most warnings come from someone who has something to gain, such as convincing you to buy their product, which they will claim is much purer than other chemicals. Of course they cost three times as much, but its worth it, right?

If you buy from established vendors such as,, etc., you'll be assured of receiving a proven, safe product. Go to reef sites like Reef Central and check out their tank of the month threads. The reefers who maintain the beautiful and healthy tanks, and dose supplements, often mention where they obtain their chemicals. Reading a number of those kinds of articles, you'll start to get a feel for where the good stuff is being sold.

10th October 2010 11:50pm
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