hello to all ive been experimenting with various diy scrubbers over the last year with limited success so decided id try and get some opinions from those with more scrubber experience so far the only real success ive had was with a 4" by 3" screen size vertical scrubber than ran about 650 lts an hour and lit by an 11w cfl bulb on one side only my next effort was fed from the sump inlet pipe with flow of approx. 1500lts an hour and screen size of around 6" wide by 3" deep - now here is where im a bit confused - as this was a larger screen I used 2 x 15w cfl bulbs but this only gave me yellow growth - burnt algae with a little green towards the very edges of screen - so I reverted to a single bulb with better results I then changed to a diy led fixture using 4 x 3w osram 660nm leds this once again turned the screen yellow until I added diffuser and moved the light further away ok so now to my problem ! I am now trying a horizontal screen that is 6" wide so same as previous and 6" long and has the same flow rate as the previous vertical one, the screen sits in about 20mm water depth and im using the same led light as before yet all I seem to get is a little green growth that seems to turn yellow after the light has been on a few hours ? so according to what ive read this would suggest the light is too bright ( 18hrs on ) ive tried raising the light and also halved on time to 9hrs - same results so is the light to bright for available nutrients ? is there a reason why horizontal wont work as well as vertical even with same flow and light ? is the screen being submerged an issue ? is there something else ive missed ? I only feed about 1/2 a cube to 1 cube max a day and have allways got 0 readings on this tank for po4 ( hanna meter ) and undetectable nitrate ( salifert ) but I do get some nuisance algae in dt so there must be some nutrients regardless of the test results and I get an almost daily green haze on the glass any advice appreciated thanks
So on your vertical LED scrubber, did you get better (green) growth when you added the diffuser / backed up the light? Usually, when you have yellow growth that's too little flow, too much light, etc. With LEDs (in that arrangement) you can back the hours way down, further than you think. For 0.5 to 1 cube/day feeding, I would have started with 9 hours/day and gone down from there. Maybe a split photoperiod also. This seems to work well greening things up when feeding is low. Too much light for too long causes photosaturation, and then nothing grows. The longer you are at photosaturation, it seems that growth reverses (die off, bleaching, burning, whatever you want to call it). I am not the horizontal expert from personal experience, so others may chime in here, but I'll tell you what my theory is based on what I've seen done. Horizontal screens still need a thin laminar flow. 20mm of water is probably too deep, all the water passes right over the screen instead of through the screen or across it. Is there any slant to it at all? I'm guessing not. Lighting may still be the same issue. Your description of green turning yellow seems to indicate photosaturation. Try splitting up the photoperiod and reducing the total "on" time. maybe something like 2 on, 2 off, or even 1 & 1. Haze on the glass is hard to get rid of in general. But with a scrubber working right, it should take several days to get to the point where you need to clean it, or even a week or so. It's rare to never have to clean the glass, but I've seen it done.
thanks for the quick reply and advice yes I had much better results in general and decent green growth with the vertical version after adding the diffuser though did get some yellowing in the middle of the screen so probably had lights on to long by the sound of things s0 after spending the last few hours trying a revised version of the horizontal with a shallower depth of water flow that then caused back ups of the water flow and other problems ive decided to revert to the return fed waterfall system and just incorporate a few mods to help make maintenance a little easier and run a shorter lighting period - will try 9 hours as you suggest and go from there ps love the rotating ring idea for locating the screen on your new scrubbers !
