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What does this growth mean?

Discussion in 'General Discussion' started by ChrisQ0904, Feb 14, 2021.

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  1. ChrisQ0904

    ChrisQ0904 New Member

    I have a newly setup algae scrubber, maybe 1.5months installed and I am getting growth but not hair algae. I was wondering if someone could help me out with what the growth is trying to tell me... Excess nutrients/lighting/flow etc. I had very little growth for a bit running reverse lighting and when it finally grew it was like a think slime, the past week I have had the lights on 24/7 and the picture is what I have at the end of the week.

    Thank you. 20210214_193652.jpg
  2. Turbo

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

    The startup phase can vary quite a bit depending on your exact system conditions. You have GHA on the base of the screen, I can see it in the pic above. There is a slime coating on top of the GHA - this is not atypical. It's usually a phase that passes, sometimes in a few weeks, sometimes longer.

    The slime doesn't harm anything once you have a base of growth. Initially, on a bare screen, the slime will inhibit GHA from attaching so you would want to rinse that off as often as 2x/week to keep it at bay. All that is needed is a swipe of the palm across the screen while rinsing.

    In your case, since you have a base of GHA, it's helpful to just rinse the screen off under room temp tap water while rubbing with your fingertips to loosen and rinse away the slime growth. Then leave whatever GHA remains attached to the screen alone, scrub the top inch to make sure that's clear of any growth, and any other general things like rinsing the false bottom and making sure the slot pipe is clear/clean, then put it back in operation.

    As for the lighting, there are 2 things at your disposal - duration and intensity. Intensity is the "instantaneous" factor, so this affects things the most - you want a balance point where the nutrients being adsorbed are matched by the nutrients being delivered, and you have to have enough of a base of growth to allow for this (i.e. to justify high intensity lighting). If you have this set too high (depending on your scrubber growth and system conditions), you can get less or undesirable growth actually. So unless you have really high nutrients, a large tank, and a mature screen you don't want this to be too high.

    Duration has less of an immediate impact on performance, it's a combination of intensity and duration that matters. What you want to find, eventually, is the point where you can run a given intensity for a long period of time to maximize nutrient uptake without bottoming them out.

    Lastly is flow - you want the flow across the screen, initially, to be just enough to cover the screen. Turn it down until you don't have enough flow to reach the far end of the screen, then turn it up until it starts to "arc" and miss the near end of the screen. Those are your "low" and "high" points. Aim for a flow rate towards the lower end of flow volume. Generally when you increase intensity past a certain point, you would want to increase flow a bit. But more flow does not necessarily mean you will get better growth, there is a point of diminishing returns w/r to flow

    Starting out with the dimming knob at the halfway point (6 o'clock) an running the lights for 9-12 hours/day and a lower-end flow rate until you get some GHA filling in. Swipe to remove slime as often as 2x/wk. Once GHA kicks in and starts to fill in the holes, and does not easily wash away with a simple rub & rinse, bump the intensity up about 1/8 of a turn (depending on when yours was built, this might be clockwise or might be counter-clockwise) and run at least 12 hrs/day. Let it go a couple of harvest cycles to confirm, then if you see progression (more GHA, even if covered with slime) then you can go to 14-16 hrs/day. A cycle or two of growth to confirm. Then alternate adding a few hours/day to the growth cycle and increasing the intensity until you get to around the 3/4 point on intensity and about 18-20 hrs/day. Then hold for at least 2 cycles, watch your tank, watch your nutrients.

    The 3/4 point is actually 50% of the intensity of the lights. The dimmer is not quite linear (6 o'clock position is 25% intensity). So going through any additional intensity increases between 3/4 and full is a big jump - take it slow, and you will want to increase flow a bit when you go past 3/4 to increase the instantaneous rate of nutrient delivery.

    On the other hand, I've had people go straight to 100% and 24/7 lighting from day 1 and get great growth. However I think these are exceptions - it's better to ramp it up. If you have a large volume and a mature tank (high biodiversity), then a scrubber will start up quicker and being aggressive works fine.

    Post your tank details, a lot of this above is very general so I may be able to give you a more specific answer with more details


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