I never understood what defines a scrubber as perhaps oversized. Says SM? What science backs that spec up? Not trying to ne a pain, just questioning. In my experience scrubbers are self regulating. that is, they can't over scrub. At the same time, a larger scrubber is better able to handle a spike in nitrates or phosphates that a smaller scrubber. Am I missing something important here?
I'm actually with you here. Yes, SM, and based on anecdotal evidence, which however 1) is sometimes all we have and 2) is usually a pretty good rule of thumb.
Interesting that you bring up the phosphate issue. Are you saying that the smaller screen kept your N down, but not P, and the larger screen kept both down? I have had the opposite effect. The larger screen could not keep P below 0.09 and the smaller one now keeps it below 0.04.
Larger screens are not necessarily better, the reasoning is that green is better filtration, and smaller screens force the algae to grow in a smaller area, larger screens spread out the growth and it gets starved of nutrients and turns yellow. There's more to it but that's mainly it. Also basing the screen size on feeding makes a lot of sense, food in = waste out (on average)
Therefore a screen that is, I would guess, 1.5x larger than the feeding based guideline is probably fine, but any more than say 2x the feeding guideline and it will probably tend to grow thinner. Pulling those figures out of my behind but that's sort of what I see happening.
Light intensity, flow, and other factors can affect your system as well, as can many other factors that are specific to your system, so what may work great for one person may not work at all for another. I can tell you this from personal experience, I have people telling me one particular scrubber grows ganbusters immediately while the exact same scrubber grows nothing for someone else.
I agree totally with your post. I tried the new guidelines and it could not keep up with phosphates in the tank. My waterfall screen is 14x17" lit on both sides lit by 40 watt spiral bulbs, one one each side. I get a gallon of algae every 5 days from it. There has been many post where it is said that the new guidelines don't remove all phosphates.
The phosphate issue is not restricted to scrubbers and is, as far as I can tell, related to the size of your screen, under or over sized, or sized correctly. I brought it up because SM is claiming it's P soaked into rocks coming out and transitioning in and out of various states and that's why it's not getting pulled down. Other non-scrubber filtration systems, even probiotic systems, in certain conditions, have the exact same issue.
So the fact that you are getting P=0 is great, are you testing on a Hanna meter or a liquid kit? It may be that your system has the right balance of input (food) and algae strains that keep everything in check. There's a lot of theories on what is going on here. It's definitely an interesting discussion if you know where to follow it.
Besides how many times have you seen an entire tank covered in hair algae and the poster can't figure out why his phosphates are zero. If the guidelines held true there the algae would cover what one maybe two rocks then? If the hair algae continues to grow why wouldn't a bigger screen grow til there was no phosphate?
Algae grows in areas of high flow, because in these areas the O2 produced is removed quickly before it grows to toxic levels and inhibits photosynthesis, and the nutrients are delivered efficiently, both of these via breaking through to the boundary layer where the exchange occurs. If you had 2 identical tanks, one with a scrubber and the other with just algae growing in the tank, I would be willing to bet the harvest would be about the same.
As for the bigger screen/P issue, is has nothing to do really with screen size as it does the fact that if there is a limitation of one or more elements needed for growth, then uptake/growth slows to match the availability of that nutrient, unless a strain of algae is present that can more efficiently grow at the given ratios supplied to it. Meaning that if you have dominant algae that uptakes N and P (and perhaps K also now) and one particular ratio, and the ratio of available nutrients does not match this, uptake stops when one is depleted or perhaps even lowered below a certain threshold. So increasing the screen size theoretically cannot fix this issue.
Floyd, can you lend some advice? I just got 2 12w LED grow lights (spot lights) you had recommended to another member. I started to hook them up but I'm confused on how close to make them. Real close and the colors dont blend, too far and it looks weak. Your recommendation would be greatly appreciated!
You should be able to remove the cover on the fixture and remove the optics, then replace the cover and put the lamp a lot closer. you may be able to just remove the blue optics and let those spread more, and leave the red optics in place - I don't know, I haven't seen one before, but I was told that is what you can do (remove optics)
FYI, that LED floodlight (if it's the one I'm thinking of) is really only good for about a 5x5 screen, and not many have used it.
