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Thread: Pete's Algae Scrubber for a Planted Tank

  1. #1
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    Pete's Algae Scrubber for a Planted Tank

    I’ve had a 180 in my living room for almost 20 years.



    All of the plumbing is routed downstairs to its own dedicated room.



    I had an MMFI algae scrubber hooked in (upper left above) until about a year or so ago until it finally fell apart. I was unable to find any new scrubbers for sale, even at this site it looked iffy, so I bought three different plexiglass adhesives to try and fix up the old scrubber. But with all of the changes in technology, both lighting and design, I tossed out the old MMFI scrubber . Like I said, I would have gladly just bought a ready made scrubber, but the only one I found was here and sales didn’t look promising. I probably would’ve balked at the price anyway.



    So I set out to build one on my own. Using some of the info here I bought the lights and two 2’ x 4’ sheets of 1/4” Acrylite. $300 already, good grief.



    The scrubber is two feet long and I cut the sides and bases such that I could get them from one four foot sheet. I taped off the base prior to applying the two part Acrylic glue. This helps to align the sides and makes the build a little cleaner.



    Glued one side on and then the other.







    The two part glue is really strong. The below picture was my first attempt that I botched. I pulled on a side to test the joint strength. The plexiglass failed before the joint!



    Here’s a picture of a bad patch of joint on the new scrubber, don’t know why the bubbles.



    The rest of the joints looked like this. Probably should have let the glue sit for a minute after mixing to get the bubbles out.



    All four sides on.



    End caps on and a water test.



    There was one leak, but not at the above suspected joint. I used the super thin adhesive to patch the leaking area and the result was no leaks as evidenced above.

    Time for an old guy on his own this week to stop for dinner.



    Time now to install bulkheads and light holders.



    Next the input water tube.



    And the lights.



    Pretty simple, really, but the plexiglass is hard to work with. It warps and is not true. You really need jigs to do it clean.



    Done, finally! Total cost is around $400, more if you include tools and the blade.



    Then of course, I had to plumb it into the system. I don’t have to worry about light leakage since it has its own room, and that lets me fiddle around with the dimensions as well. The main objectives are usefulness and ease of cleaning. The MMFI scrubber was a real difficult to clean.





    And a movie for you.

    http://www.snekpete.com/Scrubber/Srub_short.wmv

  2. #2
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    Welcome.

    Nice acrylic....

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    Nice acrylic work but dang how much for 1/4"? I buy 4' x 8' sheets of 1/4" plex-g for $150!

    Looks sized for tank volume not feeding, have you read the new guidelines?

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    Sorry, but I don't pay any attention to guidelines. Everything is trial and error. I bought the sheets from USP for ~$50 a piece, so $150 for 4'x8' sounds about right. Shipping on a 4'x8' is prohibitive. Might have been able to find a local distributor, but $50 for shipping I can live with.

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    That's a big screen! Are you feeding lots? They are real plants in your DT aren't they? Nice build but are you sure you need a Mega scrubber ? Sorry for questions, just curious.

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    Real plants indeed! I built it large because you can always adjust the scrubber by lenghtening or shortening the lighting cycle. Also, I wanted to be able to run the entire flow from the pump through the scrubber. As it turns out, I will need to replace the bottom drain bulkhead with 1" instead of 3/4" as the total flow from the pump tends to fill up the scrubber. But that will wait. The larger scrubber allows for more fiddling. It will be interesting to see the rate and amount of growth. Like I said the tank has been set up continuously for over twelve years now and with constant water changes and fertilizing it needs a big scrubber.

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    Well the current guidelines are not trial and error, they are established and accepted. The old guideline was 1 sq in per gallon of water of tank volume, the new one is based on volume of feeding, 12 sq in per cube of food per day lit by a total of 1W per sq in of screen (LxW) split between both sides. You're looking at a screen that can handle >10 cubes/food per day, and unless you're feeding at least half of that, it won't grow green very well. It will still filter, but the smaller feeding based sizing method results in more green growth faster and more consistently, and green algae does the best filtering. A scrubber that large with that much light on it is going to be an order of magnitude more efficient than your old one, and will likely out-compete your plants. Those are my concerns. Not knocking your design at all, it looks very well constructed, just making sure that you know what to expect or watch out for. FW scrubbers grow much faster also. You might want to keep an eye on plant health and adjust the photoperiod down if you need to, I would say that is the #1 thing to do.

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    Well, I've got about 200 gallons total water volume. By the old guidelines that's 200 sq. In. The screen mesh is 12" x 18" = 216 sq. In. Better a little big than a little small. And with aquariums, each setup is unique. It is more art than science. I have a mixture of well and RO fed in, about 7 gallons total per day. The quality of the well water varies throughout the seasons. I suspect that the plants will do better with the scrubber because it will allow me to add more fertilizer. We'll see.

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    Redbone - I am now officially baffled. So you have made a scrubber to mop up fertilisers that you have intentionally added to the system? Why don't you just add less ?

  10. #10
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    Quote Originally Posted by Garf View Post
    Redbone - I am now officially baffled. So you have made a scrubber to mop up fertilisers that you have intentionally added to the system? Why don't you just add less ?
    Planted tanks are by far the most difficult freshwater tanks. The balance of nutriments necessary for healthy plant growth versus promoting algae is a tightrope and is constantly falling out of balance. Cut back to reduce algae and the plants suffer. Add too much and the algae takes over. A scrubber really helps by having the growing algae in the scrubber compete with the algae in the tank. Although the plants and algae compete some, it is not like the competition between two algae . Plants, especially the different varieties that I try to grow, have very different nutriment needs from each other and from different algae.

    Also, I forgot to mention that plants, depending upon the variety, get most of their nutriments from the substrate, especially swords and lillies. Trace elements mostly come from the water column. Algae get all of their nutiments stricly from the water column.

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