Ok... I'm lazy. Super lazy. I wanted to be able to fertilize daily without actually FERTILIZING daily, ya know? So some people here in the past talked about using peristaltic pumps with timers but I haven't seen anyone actually slap together a working system and post... so I'll do it! I'll first go through a run-down of my materials...
6 peristaltic pumps from www.aptinstruments.com
. I used the OEM SP100 pumps (18rpm) w/ 1.6mm norprene tubing (about 0.9ml/min flow). i wanted to be able to dose up to 6 different wet ferts, so i bought six. wanna do 3? buy 3.
for the controllers, i got lazy... i picked up a bunch of table lamp digital timers off amazon.com. they were about 12 bucks a piece and have batteries in case of brief power outages. i put one timer on each pump so i could run them independently. if you are good and know what ratios you need to dose, you can get away with fewer. i went for maximum flexibility (at a much greater expense, though). the timers do an OK job. they have 2 "events" so you can even choose to dose twice a day if you'd like. in addition, you can easily turn them "on" for a few minutes manually if you want to dose something in particular. http://www.amazon.com/Intermatic-TB1...4121541&sr=8-1
i also ordered about 50 feet of norprene tubing from APT as well. in addition, i picked up a few 90 degree elbow connectors so i could make the tube "hook" over the lip of the aquarium.
i have a prototype shop at work, so i whipped up a small "stand" to hold the reservoirs and the pumps are attached above. you can make this out of wood, metal, plastic, WHATEVER. it is not important at all. i used 1/2 gallon milk jugs (cleaned thoroughly) because they are tall and skinny so i could squeeze them in under my stand nicely.
as you can see, each side has 3 jugs and 3 pumps. the desktop lamp timers are nice because the "controller" portion has a cord that runs back to the power strip, so i could mount everything on the door.
so far, i've been running the pumps for about 1 month and i'm very happy. i keep slowly upping the time because i think there is a lot of backpressure so 0.9ml/min isn't what the flow seems to be. something less than that. but since everything is controlled independently, i can just increase whatever i need to increase. i can easily see what ferts are running low. i just used a label maker to clearly label everything. i spray-painted the "stand" black just so i didn't have to look at the bare metal (plus i'm avoiding rust).
oh, the only downside to the lamp timers is that they aren't grouned, so you should probably ground the pumps (mine were not grounded at the time i took these pictures).
it's not perfect, pretty, or sexy... but it works! you have no idea how nice it is just knowing that my ferts get dumped in every morning before the lights go on. and the 1/2 gallon jugs hold quite a lot of ferts... so i don't have to fill them very often. the ultimate in low maintenance!
and to avoid contamination, the output tubes are NOT in contact with the water. the output tubes bend over the lip of the aquarium to hook on, but there is a significant gap between the tubing and the water. the tubes are always filled with fertilizer, so people should keep that in mind if they ever set something like this up!
all in all... maybe around 500 bucks for the pumps and timers. everything else is cheap. and again... 6 independently controlled pumps should be overkill for anyone here. i would assume most people would only dose 2, 3, or 4 different liquids.