Turf scrubbers vs. other nutrient export

[DWIZUM]

Hello all,

I've been "turf scrubber curious" for a few years, and am likely going to include one on my next tank (roughly 250g, mixed reef.)

As I'm starting from scratch, instead of incorporating a scrubber on an existing tank as seems to be the case for many people on the forum, I'd like to plan ahead for how turf scrubbers mix (or don't) with other nutrient export methods. While I appreciate the concept that scrubbers will save your tank, mow the lawn, and do the dishes, I'd also like to build a robust and balanced system.

So, can people comment on using a scrubber along with skimmers, macroalgae in a refugium, carbon dosing, etc.?

Thanks in advance.

[jgreen1025]

Well, since none of the more knowledgeable people here have weighed in with their wisdom, I'll pass on my *thoughts* (which I often confuse with "wisdom"). Besides, I think this is an excellent topic for speculation.

My original tank was skimmerless and relied entirely on biological filtration provided by the sand and rock, with chaeto, halimaeda and xenia to provide some nutrient export (along with all the snails, worms and "pods" that thrived). The chaeto eventually died out for lack of nutrients but it worked fantastically in spite of what I considered a rather high load (50g tank with 3 chromis and 2 clowns) and heavy feeding. Hard and soft corals grew like crazy and I had little nuisance algae until work interferred and rudely took up too much of my time and energy (but it lasted about 3 years).

I'm now trying to recreate that earlier success but incorporating a turf screen as well - not only for nutrient reduction but also for production of all the little critters that serve as food and cleanup, etc. In addition, I'm hoping the whole system will be a friendly place for reproduction of herbivorous snails and other desireable animals and coral. I'm a little concerned that a screen could limit nutrients too well - I'm a fan of xenia, and I'd like to include more macro algaes this time - so I'm planning to experiment a little with the screen to manage this. But basically it'll all be natural filtration (I consider algae way more natural than a protein skimmer). The only things I plan to dose are calcium and alkalinity, and silica to encourage diatiom growth for snails (and hopefully sponges). Oh yeah, and phyto for filter feeders. Basically, I want a healthier and more natural tank, with not just fish and coral but all the other critters as well.

So, that's kind of my thoughts on turf scrubbers and what I'd like it to add to my system. I think it'll take a little effort to get it to that point, but that's half the fun, right?

[kcress]

I believe generally a turf scrubber will trump EVERYTHING else for export. So most anything else will die or fade away.

Of course you can always under size your screen or dial back its power to keep the nitrate levels at some point.

[SantaMonica]

The best way to lower the scrubbing power is via the lighting period: just reduce the hours. But by building a scrubber capable of full power, you can turn it back up when needed.

[jgreen1025]

I believe generally a turf scrubber will trump EVERYTHING else for export. So most anything else will die or fade away.

The best way to lower the scrubbing power is via the lighting period: just reduce the hours. But by building a scrubber capable of full power, you can turn it back up when needed.

That was kind of my thinking - that it could easily be too effective at reducing nutrients for my wants. It's still theoritical for now (I just got it up and running again last weekend, so there's no algae on the screen yet) but it's nice to know that cutting back on lighting is an easy option if it proves too much. I think my screen is 13"x10" (double-layered, and scratched up as much as I could) so it ought to be plenty big for my 50g tank, but we'll see how it goes.

Incidentally, I was at Home Depot last week getting another clamp light for it and the guy behind me asked if it was for a reptile. I said it was for a reef aquarium and he asked more about it so I told him it was for an "algae scrubber" - and he knew what it was! Unfortunately, I didn't have more time to talk right then, but maybe that shows what a good job Santa Monica has done in spreading the word.

[DWIZUM]

Thanks for the thoughts, everyone.

Basically, I want a healthier and more natural tank, with not just fish and coral but all the other critters as well.

That's what I want, too! Though perhaps slightly lower nutrients than your comments indicate.

My system is going to be 360g, and probably rather lightly stocked. Originally, it was going to be a basement sump (plenty of room) though now I'm leaning towards under-the-stand, which means much less space. My sump will have an 18" x 12" skimmer compartment, an 18" x 24" compartment, and an 18" x 12" return compartment. That middle 24" compartment will have about 20" of space above the water line. That's the area I've got to play with - for a refugium, scrubber, both, something else, etc. So now, I need to do some more research and get a design down.

It sounds like it would be futile to put a macroalgae-stocked refugium in that middle compartment if I'm using a scrubber there, but I'm still curious about balancing a scrubber vs. a skimmer. Has anyone run a very large mixed tank (with maybe a slight SPS focus, though not a twig tank) with ONLY a scrubber, or a scrubber and an undersized skimmer? Especially considering my space constraints?

The other possibility is to go back to a basement sump, but then pumping requirements go through the roof (I'm trying to keep power consumption reasonable.)

And speaking of power consumption, has anyone else thought about nutrient export per watt? Some of the needlewheel skimmers are extremely efficient in that you can heavily skim a big tank like this well under 100w. I understand that spiral compact fluorescent lamps are common for scrubbers, is anyone using anything else? LEDs, or even T5s? I'd imagine you could drop the power consumption by half or more compared to spiral compacts.

[SantaMonica]

has anyone else thought about nutrient export per watt?

Yes, and you need to remember that skimmers don't export ANY nutrients per watt. They export protein (food). So if you want to export the most food per watt, then get a good skimmer.

If you want to export nutrients (ammonia/ammonium, nitrite, nitrate, phosphate), then that's when you can start looking at scrubbers.

viewtopic.php?f=9&t=68

LEDs, or even T5s?

No, and yes.

I'd imagine you could drop the power consumption by half or more compared to spiral compacts.

No.

[DWIZUM]

Can you explain your last "no?"

Given the right component selection, LED lighting puts out more light (PAR, lumens, take your pick) than any other type of lighting, and you can pretty much pick the exact spectrum you want by blending different color emitters. Hence I would assume that, given an ideal light profile (i.e. name your intensity, spectrum, etc.) LED would be the best choice, no matter the criteria. Meanwhile, spiral compact fluorescent lamps use inefficient built-in drivers, and by the very nature of their spiral design, there's a ton of light wasted thanks to restrike and the basic omnidirectional nature of the light output. Even T5 should be better (in terms of light that reaches the algae vs watts consumed) because you can use a good reflector design and more efficient ballasts.

Other than the mantra of "use spiral compact" is there any information available regarding the "best" intensity, spectrum, etc. of light for this turf algae to grow?

I've read plenty of success stories for scrubbers, but also plenty of "falure" stories. It's not always clear what separates the two, since often the techniques will seem similar. Hence, I have some questions about things that I'm wondering might separate the successes from the failures, beyond the typical things discussed.

I'm interested in knowing what typically limits algae growth in a system with a large scrubber and no other nutrient export. Are people seeing N and P sucked down to zero, or does one typically linger while the other is zero? This is assuming you've got the right light and flow I suppose. If you had the right light and flow, and N and P were both detectable in the tank, then I guess you'd have to look at defficiencies of some other nutrient.

I spent a lot of time measuring and adjusting levels of various nutrients in planted freshwater tanks when those were my focus, how similar are marine turf algaes to typical FW plants in terms of nutrient needs? Have there ever been efforts to supplement nutrients proven to be limiting growth in a scrubbed tank?

And what about a carbon source? Again, referencing planted FW tanks, it was very common to supplement CO2. Has anyone ever monitored O2 or CO2 levels in a scrubbed tank?

[DWIZUM]

has anyone else thought about nutrient export per watt?

Yes, and you need to remember that skimmers don't export ANY nutrients per watt.

So, if not skimming, what forms of nutrient export did you compare it to in terms of export capability per watt consumed?

[jgreen1025]

And what about a carbon source? Again, referencing planted FW tanks, it was very common to supplement CO2. Has anyone ever monitored O2 or CO2 levels in a scrubbed tank?

This article might be helpful: Photosynthesis and the Reef Aquarium, Part I: Carbon Sources by Randy Holmes-Farley where he discusses CO2 in reef tanks. (As far as chemistry issues go, Randy is THE Expert, in my opinion).

I think you said you haven't yet set up a scrubber but you have a reef tank you could try one with? Scrubbers are pretty simple and inexpensive to build, and what you learn might help in your planning for the 250g reef.