ATS For 120 Gallon Tank.

You might try reviewing the Basics in the Resources section, that will likely cover most of you questions.

For a 120g, I think anywhere in the 2 to 4 cube range should do you very well for quite a while. Especially in combination with a skimmer.

As for which comes first, IMO this really doesn't make a ton of difference. Maybe at first, when you are trying to get the algae scrubber screen to mature, but even then only if you have problems with it starting up.

Scrubber first would mean it gets first crack at the water from the tank (obviously)

Skimmer first means that the effluent from the skimmer, which is well aerated, goes to the scrubber next, and this can also have a benefit.

If you wanted the best of both worlds, you can put the skimmer in the same section with the scrubber pump, and put the effluent line from the skimmer right over the scrubber intake pump, so you will have a mixture of direct-from-tank water and aerated skimmer effluent.

 

That looks good, except that you only need one of maybe 2 zip ties. You don't need to clamp them down hard, in fact, doing so will cause the slot to pinch closed. You only really need one at the center of the screen if you trim the top edge of the screen in such a way that it touches the top inside point in the pipe above the slot - then it will keep itself level. If you cut the screen so that it is barely inserted into the slot, or only partially, then 2 at any 2 points will do to keep the screen hanging straight.

You can also use a rotatable ring made by cutting off a female/female connector, then clipping out a section so that you can snap it over the pipe and just rotate it when you need to remove the screen.

Can also use a recloseable zip tie, or a thin section of double-sided velcro.

 

Can you post a picture of the screen?

Have you cleaned it yet since you started running it 3 weeks ago?

How much water flow are you providing to the screen?

How many hours/day are your LEDs running?

 

Let it grow for at least 14 days each time during the break-in period, unless you have a bunch of slimy type growth. You will want to rinse that off, but all you should need to do is swipe the palm of your hand across the screen and rinse very gently in room-temperature tap water. You don't want to scrub or rinse away any hair algae. The initial growth of hair algae will be very loosely attached and that is easy detached, so you don't want to clean vigorously for the first few months.

18 hours/day with the amount of LEDs you have might be a bit too much right now. I would back the hours down to 10-12 hours/day, or find a way to lower the current. Maybe by putting the 2 arrays in parallel: connect both + sides to the + side of the driver, and both - sides to the - side of the driver. that will put 300mA through each array. Then run 12 hours/day. But I'm not sure how you are driving the LEDs, this might not be possible. It looks like you are using a custom driver maybe?

 

That looks like very dark algae. Almost black. When you rinse it off, it doesn't easily come off, and when it does, it's almost like flakes and the screen is bare white underneath. Does this sound right?

If so, it's a bit rare. It usually indicates a tank with very high nutrients. Also referred to as "black oil" type growth, because that's what it looks like. that type of growth is the one type that you want to remove with a brush, because it blocks light to the screen and will prevent GHA from attaching. But you only need to scrub the screen where that type of growth is occurring.

Do you have a very high nutrient tank? If so, I would recommend doing a few water changes to get the nutrient level down. It's difficult for an Algae Scrubber to get a "foothold" with really high nutrient levels sometimes. Once established, it will keep them down.

 

Yes, the slot/screen junction is one area that you need to keep completely clear of algae, so you should scrub that with a brush. You only need to scrube enough such that the first 2 rows below the slot/screen junction are clean. This allows flow to be maintained longer throughout the growth cycle. Adding a light blocker will reduce the growth in that area as well. Algae tends to want to grow there first, and over a period of 10-14 days of growing, I've found that the algae will completely cover that area and creep up onto the slot pipe as well, so you'll eventually end up needing to scrub the slot pipe with every cleaning. The light blocker reduces or eliminates that.

 

I would still consider cutting the hours back to 10-12 hours/day until the screen matures. You can also split up the photoperiod, something like 3 hours at a time, with 30-60 minutes of dark time between each photoperiod.

With the LDD drivers, you should be able to parallel the arrays together and use just one driver. Essentially what you are doing is splitting the total current evenly between the 2 arrays, so to the driver, it will still look like it is powering a single array. Connect the (+) side of both arrays to the same (+) terminal on one LDD, and the (-) side of both arrays to the (-) terminal of the same LDD. You will end up with 300mA going through each array, but you will still have a total of 600mA generated by the LDD. Then, you can continue to run longer hours, but I would still start out with 12 hours and then increase it more once you see the center of the screen starting to fill in.

The reason for this appears to be that too much light for too long will cause photosaturation: there is not enough algae to adsorb the energy from the LEDs, and whatever algae is there quickly becomes overwhelmed and stops growing. Lowering the intensity allows the algae to get a foothold, and once there is at least some algae growing, you can extend the photoperiod (keeping the intensity the same) and it will continue to grow without photosaturation taking place. So start with 300mA per array at 12 hours/day (either all in one solid photoperiod, or split up into multiple smaller photoperiods), then if you see growth filling in after a week or so, you can increase it to 15 hours/day, then 18 hours/day, etc.

Once you get enough growth such that you have to start scraping the screen to remove algae, then you can revert the wiring back to using one LDD per array, but you would then also want to adjust the photoperiod back down a bit to make sure you don't photosaturate again - so you would go back to 9-10 hours/day and give it a week or so to make sure you are still getting good growth. If you are, then you can start increasing the photoperiod again, but in smaller steps - only add 1 or 2 hours at a time, then give it a week to verify growth, etc.

What you might find, however, is that with a long photoperiod at a lower intensity, you get enough growth to handle your bioload just fine. So keep that in mind: you don't necessarily need to run at high intensity and long hours. The bottom line with all scrubbers is: how does your tank look?

 

Yes, that's usually the way to go, but it's not mandatory

Not sure what you mean, is that an autocorrect/typo?

 

I just noticed the "H" on LDD, so are you dimming these via the PWM input or just running them full?