Algae Scrubber Advanced

[Floyd R Turbo]

When describing units of measure, you can represent something that such as cm per second as cm/s (fractional) or as cm * s^-1 (power). s^-1 (s to the -1 power) is equal to 1/s.

cm to the -2 power is the same as 1/cm^2

So now that you understand that, you can confuse others by describing 0.75 as 3*(4^-1)

PS I am a big nerd

 

[salty joe]

Thanks Floyd. You might be a nerd, but you're our nerd! (;

 

[MSHUR]

Happy New year All!!
Maybe this question came up already, but what is the best way to clean screen from HA.
I use brush but its really PITA to scrub it off.

mike

 

[Floyd R Turbo]

Do not scrub the screen off at all! You only need to scrape it with a plastic scraper, and leave the growth in the holes of the screen alone. The algae mat will re-grow from the leftover algae.

You never want to scrub the screen totally clean, because then you will have to start all over again with the curing/maturing process. When I clean my scrubber screens, I usually only take about 2 passes with the scraper to get 90% of the algae off of the surface. As long as you can see most of the screen material, that's fine.

 

[Floyd R Turbo]

As an addition to the above, you do want to scrub the part of the screen that is inserted into the slot pipe. This you want to remain free and clear of algae so that water flow is not impeded. But that's really the only part that you want to scrub.

 

[MSHUR]

Thank you Bud,
Point taken

 

[rleahaines]

A positive exponent means you multiply the number by itself that many times.

A negative exponent means you divide 1 by the number that many times.


Example: 8 to the -1 = 1 ÷ 8 = 1/8 = 0.125

Or many divides:


Example: 5 to the-3 = 1 ÷ 5 ÷ 5 ÷ 5 = 0.008

But that can be done an easier way:


5 to the-3 could also be calculated like:

1 ÷ (5 × 5 × 5) = 1/53 = 1/125 = 0.008

 

[Brummie]

There's been stuff posted elsewhere that phosphate may not be that bad for a tank (within reason).It eludes to the fact that iron may be the limiting factor of algae growth in displays, not N and P as previously touted. I'm keen to see if there's any substance to this. If anyone has pertinent info, please post.

 

[_shorty_]

Interesting. Been kind of planning to try iron dosing for some time (and have a cheap test kit) but don't know much about it. Are there different forms of iron within our systems? One good, and one bad? Or is that not the case?

After reading your post, I decided to go ahead and pick up some iron tablets (ferrous sulfate - per Randy Holmes suggestion), along with my order to re-stock Potassium Sulfate that I needed to make anyway.

 

[JustinGr]

I have a question on flow. What is the optimal flow over the screen to get maxim growth, and what flow level diminishes growth. I had a bunch of flow on my screen with 18 hour light schedule, and the screen died back, and I cut flow to 1/2 and it is growing back.

 

[Floyd R Turbo]

Interesting. Most consider the 'sweet spot' to be about 35 GPH/in of screen width. I have had people run them up to 50 GPH and beyond with good results. This would be the first time I've heard of a screen dying back due to too much flow. Did you physically measure flow at the high level and what you have now?

 

[JustinGr]

No, I have a gate valve on the drain from the tank to feed the screen. I had the valve diverting 25% of the drain to the screen, I had a full screen when I ran a Maxi Jet feeding it and when I changed to the drain, I put the 25% on it. The screen died back over a period of 2-3 weeks. I then cut flow to about 15% and the screen is coming back. With 25%, I had about 1/2" of water over it (it's a ramp with a plexy trough, single side screen that is 4" wide x 10" long), then with 15%, if about 1/4" or less water level over it.

 

[Floyd R Turbo]

no help here - no experience with non-vertical scrubbers.

 

[_shorty_]

The only thing I can think of is that the water gets thicker and blocks more light? Total guess, depending on your specific light intinsity, and I kind of doubt I'm right... Algae in my experience typically likes good flow.

Or if it's dump style - too much contact with air? dumping too often? Again - total guess.

 

[Floyd R Turbo]

If dump style, increased flow should increase growth I would think. If it's a static slanted trough, then more flow might just mean the water flows right over the top of the growth as your boundary layer has effectively been compressed or reduced. A thinner layer of water means that there is more "friction" and the water moves slower and you get more boundary layer penetration and thus more contact time.

Could mean that static horizontal/slanted scrubbers have a upper flow limit. That would depend on the angle of course, the steeper the angle, the higher the upper flow limit, because as you make the angle shallower, your water column over the substrate would increase for the same flow rate.

 

[JustinGr]

This is what it is. The gate valve you see diverts water to the scrubber when closed. This was before the die-off to to much water flow.

 

[Floyd R Turbo]

There are a few other things to factor into the equation which makes my input even less pertinent. The light appears to be white LED which is not optimal, and the growth appears to be more red turf algae, which I actually scrub away. Red turf is what seems to grow better in the dump bucket style scrubbers, which is actually why they are built like that.

So I guess my previous guess is as good as any. The general rule of thumb on horizontal/slanted scrubbers is that you have to have a much higher light intensity per unit area. Also on that note your light is relatively far away from the screen so you're losing a lot of intensity. That can also be a factor. More info on the LED fixture would help but I'm guessing the spectrum and intensity are the main factors that are at play here.

 

[JustinGr]

Hi Floyd,

I switched that light out before the die off with a Rapid LED DIY kit, I have 5 of the 660 and one royal (in the center) with no optics on them. I have it at 75% power and 2.5" off the screen. The screen was red turf and doing well until I increased the flow, then I put the 660 lights on it to see if it would help, but it died back to a basic screen with almost no algae. I then reduced the flow with the 660 lights and it's growing back.

 

[Floyd R Turbo]

What are the dimensions of your screen?

 

[JustinGr]

4 x 10