setup for 550Gl re designed

[dirk_brijs]

mister santa after your comments in last design ( viewtopic.php?f=3&t=1156 )
i re designed my planned scrubber for my 550gl display tank
any comments and suggestions are always welcome.

[SantaMonica]

Yep looks great. Just have reflectors on the outside panels.

[dirk_brijs]

Yep looks great. Just have reflectors on the outside panels.

it has to be reflectors as I was intending to just use black acrylic for the box around it. On the drawing it shows transparant for viewing but it wont be in real?

[dirk_brijs]

Good thing I havent started the actual build of this design yet.
Now with the new calculations this seem way overkill?
What would actually happen with a too large scrubber?
Guess will have to go back to the drawing board and go with an about 130SqI screen which allows me to feed 10 Cubes of frozen food per day right?
Please advise

[Ace25]

I think under most normal conditions if you make a scrubber to large nothing bad happens, you just don't get the full growth on the screen. But if you have a tank that is lacking in biological surface area (ie. having 20lbs of live rock in a 100G system) then having a scrubber that is too large can become an issue because you don't have a balance between algae and bacteria. The algae will grow as long as you give it food, and release dissolved organics in the process, which under normal conditions bacteria and corals in the tank can maintain DOCs at a certain safe level, but if you don't have enough surface area for the bacteria to grow you could have an imbalance in the system where the algae becomes a contributor to problems in the tank instead of helping remove them. That is a very rare circumstance though and something 99% of people would probably never have to worry about.

I would seriously rethink using CFLs at this point and go with LEDs. I know this post was started well before LEDs really took off, but since your still in the design process I would highly recommend rethinking your lighting choice.

[dtyharry]

I do not agree with Ace25 at all on the imbalance thing. All the studies show that algae only start to release doc to any significant degree if they are left 'ungrazed'. If you are scraping your screen regularly the algae are constantly growing and not releasing excess photosynthate into the water.
The only negative to a too large screen as far as I can see is wasted electricity which here in the uk is expensive and lack of proper growth if not feeding enough.

[Ace25]

All the studies show that algae only start to release doc to any significant degree if they are left 'ungrazed'.

Please point me to "all the studies" that show this.

The studies I read show that "grazed" algae releases far more DOCs than "ungrazed" algae. Algae on screens is constantly being grazed upon by copepods.

http://www.jstor.org/pss/2835565

The release of dissolved organic carbon (DOC) by Daphnia pulex de Geer from six different algal species was evaluated using 14 C-labeled algae and analyzing the labeled dissolved organic matter. Up to 17% of the algal carbon ingested was initially lost as DOC from algae damaged during feeding. Only about 14% of the carbon from algae swallowed whole is released during ingestion. Additional DOC is produced by secretion from Daphnia and by leaching from their feces. More than 10% of the algal particulate organic carbon removed from suspension by grazing was transformed to DOC in the case of all food species except the very small green alga Stichococcus.

[SantaMonica]

Please point me to "all the studies" that show this.

There are hundreds. Just google "particulate and dissolved organic carbon".

The studies I read show that "grazed" algae releases far more DOCs than "ungrazed" algae. Algae on screens is constantly being grazed upon by copepods.

You are talking about something different. You are referring to the consumption of algae by pods, whereby the pods convert the algae into dissolved "waste". He, however, was referring to how the algae itself produces more dissolved organics when its growth slows down. Thus, less physical particulates, but more dissolved. It's very common in reef studies, especially now with ocean acidification.

[dtyharry]

Yes, when the turf algaes are constantly grazed and kept at a very short length, the inorganic carbon they fix by photosynthesis is rapidly passed up the food chain, and most of their energy is taken up to promote regrowth.
It is only when the growth is left unchecked that the photosynthate produced is not required for growth and is 'leaked' into the surrounding water in the form of dissolved organics.

[Ace25]

You are talking about something different. You are referring to the consumption of algae by pods, whereby the pods convert the algae into dissolved "waste". He, however, was referring to how the algae itself produces more dissolved organics when its growth slows down. Thus, less physical particulates, but more dissolved. It's very common in reef studies, especially now with ocean acidification.

dtharry stated that ungrazed algae releases more DOCs than grazed algae. I disagree and provided science to back it up. I really don't care how the DOCs get released, if it comes from algae leaching it directly or comes from grazing and consumption, bottom line is that algae being constantly grazed upon will release more DOCs into the water column than non grazed, especially when talking about algae in a screen/ATS environment due to it being an ideal living space for copepeds.

I understand what he is saying, when algae reaches a certain length it does not grow any longer, at which point it will release more DOCs. I completely understand and agree with that, but I do not agree that overall the algae will release more DOCs by being left alone especially in an ATS setup. By the time algae reaches its max growing length on an ATS screen I would imagine a good portion of that algae will be eaten/released into the water from copepods. If we were talking about putting a empty clean tank with no predators and a handful of algae, sure, that scenario that algae would release the DOCs more as it grows without predatation, but that isn't a scenario we can duplicate in our standard aquariums.

This gets back to the original question by the OP, can an ATS made too large cause issues. I still say yes, it is possible, but not probable under most normal conditions. Let me paint a very extreme scenario that no one would ever do just to get the point across. Put in a 10' long x 2' tall screen with proper flow on lighting on a 20G tank, feed the tank 50 cubes a day, the screen grows fantastic but the tank does terrible because there is not enough bacteria/bio filtration to handle that much DOCs coming into the system, yet you could easily have a 0/0 N/P reading in that scenario because the screen is working.