One of the questions that has been repeated raised is regarding what is probably considered the central concept behind the so-called "Upflow" algae scrubber: bubbles. Repeatedly touted as the mechanism that makes the UAS possible. Well here's my current scenario. I have an L2 UAS box on a 40 breeder with 4 clowns and a few corals. Fed decently every other day. This is the UAS Test unit that I originally built and put into service 1 month before the "public release" of the UAS concept (there was a small group of us given a "sneak peek"). It sits on top of the tank, and has water pumped into it. I have toyed with many version of bubble distributors, etc. For a while, I was running a piece of hard tubing with holes poked in it, held down with suction cups. This worked well at first but the holes quickly clogged, so there was maintenance involved. I got lazy and just let it stay mostly clogged. Algae still grew, in fact, better than ever. Recently I removed the suction cups and used a piece of acrylic with holes in it, strapped the line to the bottom of it, and tied the screen to the acrylic above it. I let this grow for 2-3 weeks. Growth was very good. The acrylic with the bubbler on the bottom and screen on the top, growing algae, floated up off the bottom. Algae grew underneath the bubble bar, on the acrylic box itself. Only light and water flow there. No bubbles. I got some video of it during cleaning, and I'll try to upload it as soon as possible. Water feed is via a Cobalt MJ900. Air pump is a mid-size regular old pump. The harvest was about 100g, squeezed. Pretty good. Conversely, I also have a 60g stock tank with 2 clowns, lots of corals, lightly fed, with a SURF2 that I picked up from a local guy who couldn't get anything to grow. I have been cleaning that unit at the same time as the UAS L2. The box is now home to at least 3 bristleworms, each at least 6" long. So I don't know how much that is throwing off this particular test, but it sure makes it fun to clean the thing. Air pump is the Fusion huge sucker that SM sells. Cranked to the max - lots and lot of air. This growth period's harvest: 4g. Four. Not 40. FOUR. I bet if I really scraped and scrounged, I could have gotten at least 6, maybe 8. But that would have probably included a few strings. I consider myself a child of science, so I can't "close the book" on this bubble thing, but if it walks like a duck and quacks like a duck, it's a duck. Right now, looking a LOT like a duck. Duck = gimmick.
Sounds right. My horizontal ain't got big bubbles, and it grows great. Back to the large bubble (CO2) delivery though, you may also suggest that the air (mostly Nitrogen) is actually a great growth medium for Nitrogen fixers such as Cyano, and therefore more likely to grow Cyano than GHA especially in low Ammonia/Nitrate tanks, but I haven't given this much thought, as I'm sure neither has anyone else.
I have been using a UAS for the last 6 months with a bubble wand - small bubbles- with the concept that the bubbles really are only the mechanism for water flow, rather than causing an interface between the algae and air. Algae grows nicely anywhere in your system you have light for it, so lighting anything and running water past it anywhere acts as an algae scrubber. In fact you can just light a portion of a sump without any additional flow and get algae growth. That said, my experience with this is that the UAS - even though twice the size as recommended for the feeding I do - didn't overcome the algae growth in the DT or really even slow it down at all. I have now installed a 2 sided waterfall scrubber as well and am starting to see some reduction in Hair Algae and Bryopsis in the DT. My opinion - the UAS and the floating scrubbers work up to a point, and probably will help to keep Nitrates in check, but they really are not that effective for a tank larger than 30 GAL no matter how little feeding is being done. If someone has other filtering going on such as using GFO and/or a skimmer the UAS or Boat may be useful to keep Nitrates and Phosphates in check, but it is not the magic that SM says it is.
I agree that UASs seem to be more appropriate for smaller systems. I also agree that the size of the units per the feeding guideline seems to be disproportionate, meaning the sizing guideline for waterfall scrubbers does not directly correlate to upflow scrubbers (UASs need to be bigger). All that being said, the SURF and HOG units are all given a rating that correlates generally to saltwater feeding rates for tanks much larger than 30-50g. Feeding 2 cubes of food per day is really quite a bit of food. 4 cubes/day is a lot. There's no way that you would or should feed a tank under 75g 4 cubes/day - if you felt the need to do so, you have overstocked your tank pretty severely IMO. So the SURF4 is clearly built to go after larger tanks. At $499 (I think he dropped this price - used to be $549, same as my L4 hmmm...) and then 2x $35 fusion air pumps. Clearly meant to go on larger systems. So who knows. Maybe I'm wrong. But the evidence does not seem to support the effectiveness of the UAS.
Just did another harvest and video today. Epic fail on SURF2 - possibly less growth than the previous harvest - definitely 5g or less. Same growth on L2 UAS tester. Definitely in the 100g range. The true test would be to put the L2 UAS on the same tank as the SURF2. So I cannot say with definite gusto and feeling...anything really...but come on, 2 back to back horrible harvests???
i really don't understand the point of building a floating scrubber. wouldn't be easier to just use a baffle in the sump to keep the water level constant? its seems like you would get more flow running acrossed it also. are you supposed to position the screeen just below the water level to mimic the water cascading down a waterfall ats? if thats the correct way, instead of bubbles under it could you just run a fan acrossed it?
To me, the main and just about only advantage of the floating scrubber is the fact that the lights can be positioned above it. This means the lights won't have the possibility of being submerged, because as the water level changes, the unit will stay...um...floating. A submerged scrubber between 2 baffles would accomplish exactly what you describe. In fact @srusso and I had this exact conversation on the phone one day when we were trying to figure out different ways of doing things, around the time when the UAS was the "mystery idea" that was supposed to be so groundbreaking and earth-shattering. I of course towed the line that "a submerged scrubber won't work" and "you have to worry about submerging the lights". The former was of course wrong, but that was based on what I was parroting from SM (who was in turn developing the submerged scrubber) and the latter is still a concern. So you still have to worry about the lighting being potentially underwater when the screen is in a baffle chamber. Hence the HOG type UAS or just the screen in the water and light on the outside - the original basic concept put forth by SM. Ok now that I'm re-reading your post it seems you might not know what the SURF scrubber is? Not sure what the mention of the fan has to do with?
i remember people were running fans on the water fall ats. thought maybe why not run a fan on a horizontal scrubber instead of bubbles. i am not sure of what the depth below the water line the screen is supposed to be? if its a 1/4 inch below the surface the fan would cause turbulence and deliver more air than the bubbles. if the screen is supposed to be and inch or two below the water line then the fan would be useless.
The purpose of the bubbles is not to deliver air but create turbulence. i.e. replacing the turbulence created by a sheet of water falling across a vertical screen. The whole "wet/dry/wet" bubble action with that nice little graphic that SM created is a bunch of bunk, but the action of air bubbling through the water does create a nicely aerated environment which I do think contributes somewhat. The initial reports were that Alkalinity did not drop in the case of a UAS. In some high-growth waterfall scrubbers, the algae would grow fast enough to suck CO2 out and then Alk was the next source. So this seemed logical that the bubbles were introducing CO2 from air back into the system to help reduce the robbing of Alk. However as I am typing this it occurs to me that the algae just isn't growing as well in a UAS, as does seem to be the case in a lot of instances (especially in those who haven't ever ran a waterfall and have nothing to compare to) so the fact that Alk uptake dropped is not indicative of a benefit of the bubbles, rather an indication of a lack of growth. I can't say this is the case for every UAS but unless you're getting massive growth AND no alk drop, you can't say that your particular UAS benefits in this manner due to bubbles. Kinda went off on a rant there. Sorry.
2 more UAS harvests. 3 weeks ago, same story. Then I forgot to plug in the lights on the L2 UAS and discovered it a week later. So I let both grow for 2 more weeks. SURF2 harvest was actually best yet, probably 20g. L2 UAS was again 100g+ easy. Today I noticed the SURF2 light wasn't on. The connection came loose. So that light is toast. I'll start a thread later this week and post all the pics and videos I've made to date. Another busy week ahead, hoping to take Thursday & Friday off.
