No Skimate

[jayDee]

I setup a new 180 gal reef tank in October after having a 55 gal reef for several years. I built a scrubber in the sump with a 20"X24" screen. Not being a total convert yet I also built a 4' tall 6" diameter skimmer, and a sulfur denitrator. Initially the skimmer produced little or no skimate, as expected. After about a month, the skimmer started producing about a half cup of dark skimate per day. Only in the last few weeks has the turf algae started to grow well on the screen of the scrubber. Now that the algae is growing well, I'm getting no skimate from the skimmer. Is this expected ?

I have little or no visible algae in the DT. I do have a bit of Cayno in 2 areas of low flow and some diatoms visible on the sand bed. Normal ?

[SantaMonica]

20 X 24 is way, way, way too big for your tank. This is 480 square inches, and would require 480 total watts to work best, or 240 total watts minimum.

Your denitrator, if working, is slowing the scrubber growth.

You should not have diatoms on your sand if your scrubber is running properly.

Scrubber growth is not really correlated with skimmer output.

I'd say you built your scrubber wrong.

[jayDee]

Lighting is 4 - 65 watt CFL's I thought that would be plenty. The screen is composed of a double layer of nylon window screen over egg crate. its mounted at a 35 degree angle and about 1200 gal/hr of water flows down it evenly. I can easily shutoff the denitrator if that's the issue. I haven't really had good growth on the screen until just the past week. Now the water is flowing down the algea covered screen insted of through it. Is there a chance that i just need to shut off the denitrator and wait a bit before doing anything else ? The screen is one sided i.e. all the lights are on the top side.

[new2scrub]

You want 850 gph of flow for a 24" screen so i would dial that back slightly

I would replace that screen with plastic canvas asap

[SantaMonica]

A 65 watt CFL bulb would be as big as your head. I bet they are just 13 watts; check them, and post a pic of them along with everything else.

Being one-sided, you need 4 times the area, and 4 times the wattage, as vertical. A 180 gal would need 180 square inches vertical, or 4 X 180 = 720 square inches for horizontal. You have 480. Too small, although you can experiment with it.

Window screen is not going to work at all, especially on eggcrate, and especially one-sided. Water is going to go right through it, as you have found. Instead, you need a solid sheet of acrylic, topped off with a single sheet of roughed up plastic canvas.

Also, the more slope you can give it, the better.

[jayDee]

The bulbs are indeed 65 Watt they are the 21" long straight ones with 4 pins, not the coiled ones. I have a plexiglass mirror mounted behind them to act as a reflector. I'll change the screen right away, and back it with a solid piece of plexiglass. I can probably increase the slope a bit without putting the bottom end under water -- Thanks for the help!

I wish I had found this site befor building my sump. I would have done a lot of things differently !