So I searched for 'Gravity' and didn't find anything. Wanted to know what you guys thought of doing a gravity fed scubber below my DT and above my sump. Pro's/Con's, any gotchas. Here's what I've come up with so far and what makes me think it might not be the way to go but would love to be talked into it. I think I read in another post Bud mention that the hf model was 50 gph/in of screen. If I have a 90 gallon tank and I want to turn over 1200 gph that means I need 24 inches of screen then correct? That's a lotta screen! Reminds me of my old SM100 replica DIY jobber I made (that worked GREAT btw!) but I guess that's not the recommended size anymore... Also, what would plumbing look like? I'm planning on drilling the tank and doing the herbie/durso/beananimal three pipe style overflow. Would a scrubber on the end mess with the siphon action somehow? Do I just slap a union valve on it and connect it over my sump? Thoughts?
You might look at this post for overflow fed bypass protection https://www.algaescrubbing.com/threads/algae-scrubber-basics.264/#post-2509 As for the flow, you have it right on the width, but the question is really what size screen do you need for your system, based on feeding. Also, do you actually have 1200 GPH of flow or is that your pump rating before head loss?
That 1200 GPH is just what I'm shooting for. Right now all I have is a 75/90 gallon stand and a dream. Although, I'm currently in talks with a person on Craigslist for a 90 gallon. We'll see what happens. Everything else is still on ebay, at the LFS, etc. I plan on feeding 2 cubes a day of food a day. So 24 sq in, so a 24in long by 1 inch tall screen?! :/ Does the height of the screen really matter that much because I'm thinking that's not going to work real well for lighting. And it's gonna look funny... "The best way to run a scrubber, for more than one reason, is to feed directly from the full siphon standpipe of a Herbie (2-pipe) or BeanAnimal (3-pipe) system" Well who am I to argue with an expert...
That post is a bit outdated. IMO the best way to run it is with a dedicated pump because it's much simpler overall for maintenance and generally safer. I really need to revise the Basics but it's way down on the list. As for the flow, I would advise you that trying to get your turnover rate solely by your return pump will probably not work out like you imagine. This is why there is such a big market for powerheads and wavemakers. If you want 1200GPH actual flow through a 75 or 90, you're going to need much more than the standard 3/4" return line and 1" drain. For instance, if you put a Mag 12 on that, which is 1200 GPH, and the return line is 3/4", and your vertical head is 48", you would be lucky to end up with 500 GPH of actual flow. I know this from experience. Danner's head loss chart for that pump is based on a 1.5" return line and doesn't account for elbows and loc-line nozzles, etc. When I ran one of those, I upped the return line to 1.25" and still had to go through a 3/4" bulkhead and the most I was able to get was 700GPH, which was borderline overwhelming the 1" drain which directly fed the scrubber screen, and I almost overflowed the tank once because of too much backpressure from algae growing into the slot (hence the need for the secondary bypass protection) Likely, the most you are going to be able to safely run on a standard 75/90 is about a Mag 9. Having one or two power heads in the tank will do a lot for flow patterns that you can't achieve with a return. Power heads would add to the turnover rate, it's just inside the tank. I would recommend the Jebao WP series, get 2 of the WP-25s and you will be able to make a standing wave in the tank that would overflow it if you weren't careful. Not kidding. I put one on a 40B and it was way overkill. I have a WP-40 on my 120 and I can make a 1" standing wave in there with only the one.
I didn't realize that powerheads figured into the flow rate. But that's good because I have two 1600 GPH power heads from my old tank. They're not Jebao but they ARE from China! They're also not wavemakers just constant flow powerheads. Hmm, time to upgrade! Ok, well if dedicated pump is the way to go, dedicated pump it is. That simplifies alot, I was just figuring the less noise the better. The tank will be in my home office about 2 feet from where I sit for 9-10 hours day and I'd rather hear it as little as possible especially when I'm taking great pains to make the rest of it quiet. Any recommendations on a quiet pump?
I just mention the Jebaos because they do a pretty good job of moving the water for the price, even as a static-speed power head. I have found that the Mag pumps are pretty noisy, but the Rios are pretty quiet as long as you use the bracket and suction cups that come with them, the noise is pretty well isolated. Usually the noise comes from the clot pipe vibrating against something, this would not be an issue with a gravity or overflow fed system so that's worth considering. You just have to make sure you have a contingency plan for the worst-case scenario.
