UAS or WAS?

[klaus]

Hi,

I'm planning a reeftank of about 1000L display and 400L sump, frag, refugium (about 370 gal total).

After reading through a lot of the threads on this forum, I'm convinced the system will benefit from an AS. I'm planning to let the AS drain into the refugium which in turn drains into the display (all with no pumps in between, increasing the survivability of pods). So the AS will be a separate acrylic box fed by the return pump(s) wich deliver 8000 L/hr of net flow (2100 gph).

I'm making the box myself and dimensions can go up to 150cm wide by 30cm high (59inch wide x 12inch high) lit on both sides with 660nm LEDs. There are no constraints towards building either one of the systems, both are possible and viable in my setting.

Creating the AS this big is due to maxing out the dimensions to have sufficient capacity for an sps dominant heavily stocked tank with an automatic continuous feeding system. In essence, I would like to feed the maximum until the AS can't keep up with the nutrients.

The question i'm struggling with is wether to go with a UAS or WAS. I have enough flow for a WAS with 130cm of screen and an UAS would roughly be the same screen width since I would add a bubble catcher chamber before the drain into the refugium. Such a screen would theoretically allow me to feed about 130ml/day (40 cubes) if I calculated correctly.

In the end it comes down to the question wich of the two systems would offer the best performance.

Any advice and/or opinions are welcome.

[kerry]

I have had both and IMHO I have not had good luck with the UAS in a large tank. It works great on my 10G but I was unable to get good results with it on my 150G even though it grew handfuls of algae. I gave it a go for many months but just recently built and installed a WAS on it 17 days ago. In this time the nitrate has went from 40ish to 10-20-ish. Phosphate was over "1" and now its under .5 but not yet to .25. So the WAS is working great for me on this tank. I would recommend building the screen to what you are feeding immediately and leave room so you can increase the slot to you can add more screens later. Over sized screens don't filter well at all.

[SantaMonica]

Welcome.

Practically, it's only going to matter based on how well you build and run it. Theoretically, the upflow bubbles would help with CO2 delivery.

There is no limit to the size; the bigger it is, the more you can feed. For fun, try to see if you can feed 1 pound (2+ kg) wet weight of food per day, and also keep 10 pounds (20+ kg) of algae in the scrubber at all times, even after a cleaning.

Redundancy is important, however; no matter what happens to one part of the scrubber, the remaining part(s) should still be able to operate.

[RkyRickstr]

Im right on with kerry.. had same results with uas, but waterfall is working flawlessly

[kerry]

I gave 150G UAS more then an honest go Rick. It grew 3D algae 2+" thick on each side on two 5x5 screens, one on each side of the HOB filter. I have never had a WAS grow so much 3D algae as I did in the HOB UAS. By the amount of harvest you would have thought it could filter very good. On my 10G tank the UAS does perfect!!!!! Not sure what the deal is, these are still new and still have a way to go so maybe someone will come up with a reason.

[SantaMonica]

The thick 3D might have been capturing too many food particles, whereas in a waterfall the particles would flow past it. Solution would be more rapid bubbles.

[klaus]

Hi,

Thanks for the responses so far.

It seems that UAS is indeed a solution for smaller tanks and not (yet) so for the larger tanks (coming to this conclusion on your feedback as well as reading up on other experiments with UAS, Floyd comes to mind). Still I can see the logic the bubbles delivering a steady supply of CO2 to the algae.
I'm quite the novice on this subject but after reading it all through I seem to think that waterflow might be an issue. A WAS delivers 35gph for each inch of screen, no air bubble is ever going to produce that flow. So might it not be related to delivering the nutrients to the screen that plagues bigger tanks with an UAS? Afterall, big tank means alot of volume to go past the screen until all nutrients can be absorbed. This might explain why smaller tanks have adequate results since there is the minimum size for a screen. The minimum size may have over capacity for a nano as it is which could negate the lower flow.
These thoughts led me further to contemplating an "upflow downflow algae scrubber" (or UDAS for you fans of acronyms). By this I mean, upflow bubbles and downflow water flow which is how many skimmers operate: water flow against the bubble flow to keep the bubbles longer in suspension and in the case of an AS: longer in contact with the screen.

For my specific setting I would like to keep my options open. Meaning it would be a shame to invest in any of the designs only to find after a lengthy test period that it does not work. So I came up with a rudimentary design that I've attached below. With the size limits in mind (150cm wide by 30cm high; 59inch wide x 12inch high) and Kerry's remark that oversizing early on yields bad results, I'm thinking of creating 3 separate boxes of 50x30cm (20x12inch) each with a 40x25cm screen. This way I can start with one box and upgrade as the tank matures, it eases the cleaning with the less sizeable boxes and I can alternate cleanings (do a box every 5 days for instance).

I would implement them as a WAS with a slot pipe and suspended screen but also with a bubble catcher and a drain with a port that can take a stand pipe. This way I would have a WAS if there is no stand pipe in it or change over to a UAS by adding a standpipe and an airstone and by fixing the screen at the bottom/airstone. I could even do an in between by introducing a half height standpipe. (I do hope the images do a better job to explain than the preceding sentences).

This would allow me to switch between modes or even have a mix of them at the same time (one WAS, one UAS, one in between for instance) and see what works best...

I'm very curious to hear what you guys think of it :-)

UAS mode:



WAS mode:

[kaskiles]

... an "upflow downflow algae scrubber" (or UDAS for you fans of acronyms). By this I mean, upflow bubbles and downflow water ...

I think that is called countercurrent, so maybe CCAS?

[klaus]

Well, it certainly isn't my intention to create a new type, I'll leave that to SM and the experienced scrubbing enthousiasts. I just want to end up with the most performant system for the setting I have in mind.

Hopefully the idea of having a scrubber that is capable of doing both UAS and WAS is viable. The WAS part of it is probably ok and I'm hoping that a UAS with countercurrent flow is capable of growing algae and maybe even work great for a 260 gallon tank. Having 3 of these in the long turn would allow for side by side testing as well as having different types running at the same time.

Any remarks are welcome.

[SantaMonica]

Build one and try it.