I have a 560 gallon display. Along with the display I have a 175 gal sump (not totally ful) 65 gallon fuge/settlement tank, 40 gallon frag tank, and the external overflows are quite large.. they hold 15 gallons each. The total water volume of the system (after taking out sand and rocks) ends up being about 800 gallons.. at least thats what I calculate after years of adding calcium and alk two part. It seems pretty spot on.
So.. I have a monster ATB x-large cone skimmer. I do large carbon dosings via vinegar to keep the N&P in check. I've removed GFO 1+ year ago, although I do still run carbon. Top off is done via a kalk reactor. Although I can't really complain about the carbon dosing and the skimmer extraction, the more I experiment with the tank, the more I realize I'm completely underfeeding it. I can stimulate massive coral growth by feeding it "properly" but then I end up with an algal outbreak in my fuge and even worse, in my frag tank. I see very few signs of algae in my display because the tangs eat it all. I do see it on the glass, and I have gone through really horrid bouts of red/purple turf algae on my rocks. I'm aware the is most likely happening from phosphate leach after a large phosphate absorption/equalization.
So even though the skimmer works, I'm *seriously* considering building an algal scrubber.
The first thing I struggled with is cost. The materials I'm not worried about, its the consumables. Lets assume the standard parmeters that I've read here on the forums. Lets also start with the premise that I want to install the scrubber over the top of my sump which is not under my tank (I have a fish room). Sump's inner dimensions are 24" wide, 36" long (Its quite deep). I'll need 600 sq inches of screen, and 600 watts of light. I plan on building t5ho light boxes and sandwiching them between screens.
If I have 3 screen 22" long, 16(ish) inches high, with two light boxes between the 3 (ie screen, light, screen, light, screen) I yield 1056 sq inches, but because the ends are only half lit, that really yields 704 sq inches equivalent. That yields approx 13 bulbs per "light box" assuming I can actually construct something where I can mount them that close together. That's 312 watts per box, 724 watts total. Do these calculations make sense? More specifically, can you use these wattage calculations where the light box is throwing light 2 directions and not using a reflector?
I would use 3 separate pumps one for each screen as I don't want to drill my sump again. 3 pumps makes buying small submersibles easier. 22 inches per screen 35 gals per inch means 770 gallons per screen. Thats 3 mag 9.5's.
Total power consumption per day running pumps 24 hours and lights 18. 93x3x24 = 6696 + 26x24x18 = 11232 = 17928 watts or 17.928 kW per day. cost here in Illinois after taxes is 13 cents per kW. So thats $2.33 a day or $850 a year to run.
Its not quite that bad though. I currently do 50 gallon water changes once a week. I assume I'm going to alter that to once a month. I'll save 39 water changes or 9.75 cases of salt. $55 a case. Thats $536 savings right there. Skimmer pump draws 80 watts so I'll save another $91.
So it.. in theory, will cost me only $233 over what I currently pay... which isn't that bad. I can deal with that.
So my first questions are
1) Are my rough numbers correct?
2) Are the double sided light boxes feasible? Main reason I want to use them Is I can always construct a third with one more screen and wham, instant larger filter. The thing becomes modular.
3) The sink in the fishroom I'll be cleaning these in is 21"x21" and 12" deep. I want cleaning to be relatively easy. I'm assuming each spray bar will have 2 11x16 inch screens?
Thanks for your input.