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Thread: Failed Algae Scrubber

  1. #1

    Failed Algae Scrubber

    Hi There, I recently built an algae scrubber in order to remove nitrate from my system. My scrubber is not growing lots of algae, there is a bit of growth but nothing close to an amount that I could harvest. Any ideas? Here are the specs:

    The mesh is 4ft by 15in (1.2m x 38cm) it's 3 layers of plastic canvas.
    Water is supplied to it by a 3/4 HP pump, which runs at 80-100gpm, the water runs over it fairly evenly
    6 grow-lux bulbs (3 on each side) 40w each, they are on a timer from 7am to 5pm, no part of the mesh is further than 3-4in from a bulb.

    I've tried reducing the flow significantly and that only helped a bit.
    The screen has been ruffed up significantly with the whole saw method.

    Thanks, Chester

  2. #2
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    Re: Failed Algae Scrubber

    Well let's see some pics of the screen before cleaning, and of the flow off the bottom, and of the display. I'm assuming the system is 500 to 1000 gal.

    How many weeks operating?
    What color has the algae been so far?
    Been cleaning every 7 days, all the way down to the plastic?
    Amount of food per day?
    Tests?

    I can say from the numbers so far that your 720 square inch screen is underpowered with only 240 total watts of fluorescent light. Minimum should be 0.5 watts pers square inch, and goal should be 1.0 watts. Yours is 0.33 (mine is 1.0) If you want to keep the current wattage, you'll want to reduce the length of the screen (and slot) by 6 inches per side so that the majority of the screen is in the middle of the bulbs. The ends of T5/T8 bulbs drop off in power and leave the screen underpowered there.

    Your lighting period, 10 hours, is far less than the recommended 18 hours. A certain problem. If you can't increase the hours, you'll want to increase something else (probably wattage) by 45 percent to make up for it.

    Also, you might be losing 20-30 percent of your light in the 4 inch distance, depending on the reflectors. Will need to see pics. A T5 or T8 can go right up against the screen (mine is 1.5 inches).

    Reduced flow won't do anything. Flow is already reduced in-between the layers.

  3. #3

    Re: Failed Algae Scrubber

    I'll post some pictures tomorrow, the tank isn't here at my house.
    Its 1200 gallons, but not a reef tank, it just has species from the Northern Atlantic.

    Its been running for 6 weeks, about 2 weeks ago I reduced the flow
    the algae has been a very thin brown slime
    I haven't been cleaning it because there is so little algae

    I've been feeding about 1/4 cup of squid 4 days a week.

    PH 8
    Salinity 35%
    Ammonia and Nitrite 0
    Temp: 67F - maybe this is part of the problem.
    Nitrate, very high, I don't have the number with me

    So, I will at least double and preferably triple the amount of light. Do you know the lumens requirements? I see that various 40w fluorescents put out different amounts of lumens. I'll set it to 18 hours tomorrow.

    Since I'm going to go out and buy new bulbs.... do you recommend a bulb? What wattage should I get? The ones I have now are T12

    I'll get back with pictures tomorrow. I will also get more exact measurements on how far away the bulbs are, they may be closer than I think.
    Thanks, Chester

  4. #4
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    Re: Failed Algae Scrubber

    Remember go for warmer white on the bulbs. 2700K or there about.

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    Re: Failed Algae Scrubber

    1200 is another surprise; almost 2X the screen size. But the amount fed is the real control. You are feeding about 8 oz of blended-equivalent food a week, which is about 28 ml a day. This is not much at all. So you may not need a full-sized scrubber.

    Another important factor is what happens to food particles, and fish waste, when they fall. Worst case is you have a course substrate that collects it and lets it rot. Best case is you have a bare-bottom display, with a clean up crew to break waste/food up into dust, and a strong flow pointed at it to kick it up into a filter somewhere. So do include pics of the substrate.

    Thin brown slime, after 6 weeks, just seems to point to low light energy. If it were a black oily sheet, then the problem would be different.

    I haven't been cleaning it because there is so little algae
    Biggest mistake. Clean it no matter what. Every 7 days. The new "layer" of thicker algae cannot attach to the screen until you remove the current stuff.

    Measure phosphate if you can.

    Temp is not an issue.

    Gro-Lux bulbs are ok, but I got getter results with 3000K regular bulbs, and they are cheaper. The T12 version would be:
    http://www.bulbs.com/eSpec.aspx?ID=13137

    Easist fix first: Try this and see if it works: Put 500 total watts on your current 720 inch screen. This is about 12 bulbs, and 37,000 lumens. If you start getting green after four weeks, let it keep running this way. If not, go to 720 watts which is 18 bulbs and 54,000 lumen. This is the 1.0 watt per inch level.

    Complete fix: If the above fails, go to the recommended screen area of 1200 (two-layers is OK), and increase total watts to 1200, which is about 30 bulbs, and 90,000 lumens. This will be the recommended high-filtering level of 1.0 watts per gallon, and 1.0 watts per inch. No nutrients will be able to escape this filter.

  6. #6

    Re: Failed Algae Scrubber

    After just one day of the longer light cycle there is a lot more algae.
    I couldn't figure out how to post images so here is a link.

    http://www.flickr.com/photos/46542820@N ... 349321468/

    The bulbs can definitely be moved closer. There is some green algae growing now, and some black....
    There are two upclose images of the screen, one is before cleaning, one is after.
    Most of the screen is empty because I reduced the flow, cutting off the water from most of the screen. (its running at full flow now)

    I know that this scrubber is only half the size that is necessary. But I wanted to start with a smaller one before investing in a larger one. I put this one together on a very small budget and I had most of the materials before starting. Plus I don't have a large bio-load on this tank - as you can see from the pictures.

  7. #7
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    Re: Failed Algae Scrubber

    I posted the pics for you. There is an "upload attachment button below".

    Ok is clear now. Rocks substrate collecting waste which rots. So nutrients will be higher even with low feedings.

    Distance of the bulbs is fine. You can line the walls with foil for reflection if you like.

    Screen is too smooth. It should be so rough that some of the holes are almost filled in:





    ...this is important, especially considering your (thankfully) high flow. So remove the screen (yes you will lose the growth) and dig down hard with the hole saw until you almost cut through the material. This is the single most important fix, and may take a whole day. When done, the little snags on the screen will start show gha in a few hours, and will REALLY hold on to the thick growth that will occur later.

    So just keep the current bulbs for now, and see how it looks after 4 weekly cleanings. The screen should be completely covered in growth, and most of the middle parts should be green.
    Attached Images Attached Images

  8. #8

    Re: Failed Algae Scrubber

    Ok I've ruffed it up, I'll report back in a few weeks. I have an experimental algae scrubber being tested now, if it works I'll let you know about it.
    Chester

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