There aren't that many examples of peristaltic pump dosing, so here's how I set mine up.
Here you see some emptied out peroxide bottles, holes drilled in the caps for the dosing line. The inside is standard LDPE RO line, connected to a "hose connector" which bridges onto the Tygon lab tubing. The taller bottle is 1L whereas the smaller micro and macro bottles are 500ml.
These are APT Instruments peristaltic pumps, the "topoff" pump is an SP-200 that runs at 15ml per minute and the other two are the SP-100 running at .5ml per minute. The ID of the norprene hose is 1/8th whereas the ID of my lab tubing is 3/16, so you see another set of bridging here, this time using reducing connectors. I chose slow pumps to increase dosing accuracy. I also can then have my solutions at full strength in the case of Flourish, or at the limit of soluability for the macros. The macro line is stained blue from the single drop of Methylene Blue added to the mixture used to help inhibit fungal growth.
This image is left for historical purposes, this series of connections is no longer in use.
This is basically a work in progress. If I were to do it again I'd have separate lines into the CO2 reactor, but this setup does work fine*1
The line at the top is the "topoff" line that runs through flushing the line of micros and macros.
The checkvalves are the "liquid/gas" from US Plastics, all other fittings and tubings are also from US Plastics.
Right now I have the dosing pumps set that the macro pump runs, the topoff runs to flush the system, the micro pump runs, and then the topoff pump runs again to flush the system. I've had it setup on the standard EI 3X weekly settings, but recently switching to dosing daily.*1
Both pumps run daily for 15 minutes dripping full strength flourish and EI level macros into the aquarium water from above. *3
Image of dosing 'nozzle' added December 2008
The biggest thorn in my side has been the pathetic quality Grasslin timers I've been using to regulate all of this*2
. They seem to reset themselves at will despite replacing them through Drs Foster & Smith. I will likely just purchase an Aquacontroller Jr to control the pumps and all other items that need timers.
The topoff didn't quite work as originally planned, I have a float switch, but it was so big and ugly and prone to slipping, so I never implemented it. It also didn't occur to me at the time that to topoff my daily evaporation that it would take 4 hours with a 15ml per minute pump -- in my defense I bought the pump before I had the aquarium running. In any case, eventually I will actually make it a topoff pump, but for now it's more of a "multi purpose doser." Right now it's dosing plain water to flush, but in the past I have used it to administer excel dosing, extra potassium, and the staining of the tubing is from dosing a light "gh builder" solution. I like having that versatility. In the near future I will be setting up a 5 gallon bucket to do more of a real topoff though, the pumps are basically silent so running for a few hours to slowly topoff isn't really a problem.
Questions are welcome (so are constructive criticisms).
*1 This approach was abandoned due to the checkvalves clogging. Solutions drip into the tank from the rim now and the use of a flush pump has been discontinued.
*2 Analog 15 minute increment timer is now used successfully instead of flaky digital timer.
*3 Dosing nozzle added in December 2008 in response to clogging issues.