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Freshwater Planted Tank & Algae Scrubbers

Discussion in 'Basic Principles' started by Allen Repashy, Dec 9, 2012.

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  1. Allen Repashy

    Allen Repashy New Member

    Sorry if this has been covered before.

    I am considering trying this out in a freshwater system with planted tanks. I understand this may be a difficult balancing act. Tank is low light and no Co2, It is a high flow 125 gallon river tank with directional flow 2500 Gph (10,000 lph) I am heavily feeding this tank and even with all the plants (they are not fast growers) I am not happy at all with the nitrates and phosphates at the time of my weekly 50% water changes. I am struggling quite a bit with hair algae in the tank. I don't have the time to change the water 2x a week and I don't want to reduce feeding. My tap water is high in nitrates so water changes don't really help much to start with, even if I mix it with 50% R.O.) Here is a short video of the tank.

    I am feeding approximately 2-3 grams of high protein/fat food each day. This is the dry weight because I am feeding a gel food. This would equate to about a an ice cube size chunk of finished gel or comparative size chunk of frozen.

    If I end up with an over sized system, or need to allow some nutrients for freshwater plants in the water column, I understand you can reduce the lighting, but wanted to ask some basic questions about this method.

    How long can the algae survive with the lights off and pick right back up when they go on? .... Can you run 12 hours on and 12 hours off? 8 on and 16 off?

    My thought in a planted tank is to "clean" the tank at night when the lights are off. During the day, the fish feeding in the AM would load up the tank and the aquatic plants can pull nutrients from the water. At night, the scrubber could process excess nutrients..... Is this a valid concept?

    If so, then having a big scrubber that could pull a lot out in a short amount of time would be ideal... as in over sizing on purpose to insure it can pull nearly all nutrients out overnight.... but this would all hinge on the scrubber being able to remain idle during a good part of the day.

    One option would be to have it cycle off and on every hour or two to keep the algae going, but this would not accomplish my goal.

    The other option would be to run an undersized system 24/7 that always leaves enough for nutrients for the plants, but this likely won't get me to near zero nitrates and phosphates.

    Lastly, how long can the algae survive in a power outage when you are getting no water flowing over an established screen?

    Thanks, Allen
  2. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    Allen, great questions. I moved your thread here to a new topic, the "questions about Turbo Algae Scrubbers" was really meant for product-related questions. Yours is more of a principle-related question.

    As for planted tanks, it has been done and as you allude to, it is somewhat of a balancing act. You don't want to scrub too much, but this can be controlled by varying the light cycle and also the flow over the screen. There is a good write-up on freshwater planted tanks and scrubbers on the Algae Scrubber site here:


    He seems to have much insight into this subject, and his thread sort of turned into a dissertation on planted tanks in general - worth the read.

    But he basics of it, you seem to understand already (the solutions I mentioned above). To answer your questions:

    I don't know if anyone has experimented to see how long a partially or fully grown screen would last before the algae started detaching due to lack of light, but I would think it would last several days as long as water were flowing across it. The initial guidelines said to run lights 18 on / 6 off, then the "double light" guideline came out that said 9 on / 15 off. You probably could run once every 2 days at night only for 8-10 hours and be OK.

    Your "running at night only" concept would be fine too. Again this all depends on total amount of light and flow, roughness of screen, etc - many factors at play.

    Regarding how long the screen will survive in a full outage, this again depends on the setup. An enclosed-box scrubber like the ones I make will last longer than a screen that is hanging in the open simply due to evaporation. An upflow scrubber would last much longer without water or light because it is submerged, but IMO this is still an experimental concept and not good for dedicated filtration, and especially not proven effective for larger tanks, again, IMO.

    Also here is one of my customer's threads


    He has 3 of my scrubbers, all on freshwater tanks, he would be a good person to ask about the strength of the units and how well they can control nutrients, at least in non-planted tanks. He hasn't registered on here yet so I'll have to bug him to do that and give you some input.

    But, I would think that if your goal is to reduce your need to do PWCs, or possibly eliminate then all together, then it's just a matter of putting one on and getting it to start performing (give it a few months to kick into full gear) and then when you reach your "happy point" of nutrients, and you don't want it to go any lower, start backing off the light and/or flow and just monitor everything closely for a period of weeks or months. If you clean the screen entirely every week you may have somewhat inconsistent nutrient levels, but on the average you should be able to maintain them within a certain range. If you clean 1/2 of the scrubber every 3-4 days you will have more consistent levels.



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