Mega Powerful Nitrate and Phosphate Remover - DIY!

[cvermeulen]

Duty cycle. If screen X has a constant light for 18 hours, and screen Y is rotating and only gets light for half the time during that same 18 hours, then it's only getting 50% of the light of X. That's why it won't work, or will work only half as much, which basically is not working.

Sometimes I wonder if you even read my posts before responding. Take away point - NO, there is no functional difference that you can factually represent between a 5 minute light cycle, and a 24 hour light cycle, provided the same amount of light reaches the screen on average.

Unless of course you, or someone else actually reads what I said, can come up with some biochemistry, instead of arithmetic to back up your point.

 

[cvermeulen]

Now that I've vented some frustration, let me elaborate.

You're suggesting you would rotate the screens between lights AND turn them off for 8 hours at night, when nobody mentioned this - any rational person would leave the lights on 24/7 if the screens were already rotating from lamp to dark and back.

You're also suggesting that the screens would only be exposed to light 50% of the time, which misses a great number of possibilities. Suppose you have 3 screens and 2 lights, so that the screens get the same 66% duty cycle you seem to have arbitrarily come up with. Now will it "work"? of course it will. It will also "work" with a 50% duty cycle, but it will only get 75% as much light as it would with a 16/8 duty cycle.

You also totally ignored the idea that a 6 hour on, 2 hour off, or even a 6 minute on, 2 minute off light cycle should be similarly effective as a 16/8 light cycle.

Aaaand to wind up, you still have not provided any factual evidence that a 24 hour constant running light is not equally effective, or even more effective, than a cycling light. (although other people have made reasonable points supporting this to some extent.)

Please take the time to understand what's being said before you rattle off some half assed reply.

 

[kallmond]

Has anyone identified what type of algae this is that grows on the screen?

 

[SharkAquarium]

Exactly. Just build a large scrubber screen in a tank. You can easily fit 4000 square inches in a 36 tall X 96 long tank, and just attach the lights to the outside of the glass.

Wonderful ideas.

What do you mean by " just attach the lights to the outside of the glass."? Run 8" floresents horizontally, outside the glass, MID tank level? or above?

g




Exactly. Just build a large scrubber screen in a tank. You can easily fit 4000 square inches in a 36 tall X 96 long tank, and just attach the lights to the outside of the glass.

 

[the_deeb]

Great thread. I can definitely see the utility of this for a SW setup, but in a FW setup, what benefits does an algae scrubber offer over a planted sump with emersed plants? It would seem to me, based on plant choice, that emersed plants would potentially require a less technical setup, less light and less cleaning since a continued growth would allow a longer period of nitrogen incorporation into the plants between prunings (no worries about algae sloughing off and reducing efficiency/clogging up the system).

I realize that in marine ecosystems macroalgae are the best candidates for nitrate/phosphate removal, hence the relevance of the algae scrubber, but in freshwater ecosystem emersed plants seem to predominate. Based on people's results in this thread, I believe that an algae scrubber can work on FW setup, but is it really the best option?

Thoughts?

 

[cvermeulen]

Great thread. I can definitely see the utility of this for a SW setup, but in a FW setup, what benefits does an algae scrubber offer over a planted sump with emersed plants? It would seem to me, based on plant choice, that emersed plants would potentially require a less technical setup, less light and less cleaning since a continued growth would allow a longer period of nitrogen incorporation into the plants between prunings (no worries about algae sloughing off and reducing efficiency/clogging up the system).

I realize that in marine ecosystems macroalgae are the best candidates for nitrate/phosphate removal, hence the relevance of the algae scrubber, but in freshwater ecosystem emersed plants seem to predominate. Based on people's results in this thread, I believe that an algae scrubber can work on FW setup, but is it really the best option?

Thoughts?

Depends I think. The plants require a significantly larger space and amount of structure to nurture properly, they also need judicial trimming, and may be more sensitive to the light cycle. Some plants require a substrate to grow in, and have more complex metabolisms than the simple CNP requirements of algae. If you have a heavy bio load like most of us do, getting a large enough plant population to process the waste requires a lot of space. A few square feet of screen and a few lights is sometimes an easier thing to fit.

As per the amount of light - well that's an interesting question. Plants have more complex respiration and photosynthesis processes than algae so maybe they will continue to remove toxins with less light, using other things for energy. However, In the absence of better information, I would generally subscribe to the idea that each measure of light reaching a plant cell and being used for photosynthesis would correspond with a unit of waste removed. In other words more light = more waste removal. If more light burns a plant, then maybe it's not well suited to waste removal?

 

[Toddo]

Man, finding info pertaining to the best photoperiod of algae is difficult. I found this quote from Drs F&S site....

<< For best results, give your scrubber 18-24 hours of light daily. This extended photoperiod allows the macroalgae ample time to convert carbon dioxide into oxygen. If dark periods are too long, macroalgae uses most of the available oxygen and releases excess carbon dioxide, resulting in a pH decline >>

So apparently, there is a downside of pH fluctuation if the dark period exceeds 6 hrs. (if this quote is accurate)

Just did the 6th screen cleaning and my Nitrates and Ammonia are still in check....

 

[the_deeb]

Depends I think. The plants require a significantly larger space and amount of structure to nurture properly, they also need judicial trimming, and may be more sensitive to the light cycle. Some plants require a substrate to grow in, and have more complex metabolisms than the simple CNP requirements of algae. If you have a heavy bio load like most of us do, getting a large enough plant population to process the waste requires a lot of space. A few square feet of screen and a few lights is sometimes an easier thing to fit.

As per the amount of light - well that's an interesting question. Plants have more complex respiration and photosynthesis processes than algae so maybe they will continue to remove toxins with less light, using other things for energy. However, In the absence of better information, I would generally subscribe to the idea that each measure of light reaching a plant cell and being used for photosynthesis would correspond with a unit of waste removed. In other words more light = more waste removal. If more light burns a plant, then maybe it's not well suited to waste removal?

Good points. Space does seem to be a key advantage here. Though plants are arguably more aesthetically pleasing so it might be more feasible to incorporate them as a visible part of the display rather than a gross-looking wall of algae that you probably want to hide under your stand But if space is really an issue (eg. the whole thing has to fit under the stand) then I can see the scrubber having an advantage.

You mention "the simple CNP requirements of algae" - is it known that algae do not need micronutrients?

Also, while it makes sense to think that 1 photon = 1 unit of waste removed by either plant or algae, doesn't that only really directly apply to CO2? I imagine nitrogen consumption is regulated by the rate of amino acid synthesis, which I don't think is directly coupled to photosynthesis, though I suppose photosynthesis is supplying the energy so they are indirectly linked. It would seem to me that amino acid synthesis (and therefore nitrogen removal) could occur all the time even if photosynthesis was not currently ongoing (switching between photosynthesis and respiration).

Being a more simple organism, algae are probably more efficient at photosynthesis than plants, but from a prespective of nitrogen incorporation wouldn't growth in all parts of a plant be relevant (even the non photosynthetic parts such as stems and roots) since they would essentially represent reserves of nitrogen. I guess it would be important to know what relative rates of amino acid synthesis are between plants and algae. Since plants undergo more complex growth than algae perhaps they're more metabolically active with regards to amination and protein synthesis?

Consider that a hydroponically grown spathiphyllum will maintain steady growth with just the ambient light from a nearby window. Presumably the protein synthesis that is supporting that growth must directly relate to the removal of nitrogen from the water. In contrast, with similar levels of ambient light it seems you wouldn't be able to grow any algae on a scrubber at all. While each photon of light may relate to a unit of waste removed, why do you need so much light to support the algae?

 

[cvermeulen]

You mention "the simple CNP requirements of algae" - is it known that algae do not need micronutrients?

I don't know enough about botany and biochemistry to answer that conclusively. All the wastewater treatment literature I've come across has spoken only of the CNP balance, however it could be that wastewater has enough other nutrients that it's not an issue.

Also, while it makes sense to think that 1 photon = 1 unit of waste removed by either plant or algae, doesn't that only really directly apply to CO2? I imagine nitrogen consumption is regulated by the rate of amino acid synthesis, which I don't think is directly coupled to photosynthesis, though I suppose photosynthesis is supplying the energy so they are indirectly linked. It would seem to me that amino acid synthesis (and therefore nitrogen removal) could occur all the time even if photosynthesis was not currently ongoing (switching between photosynthesis and respiration).

Being a more simple organism, algae are probably more efficient at photosynthesis than plants, but from a prespective of nitrogen incorporation wouldn't growth in all parts of a plant be relevant (even the non photosynthetic parts such as stems and roots) since they would essentially represent reserves of nitrogen. I guess it would be important to know what relative rates of amino acid synthesis are between plants and algae. Since plants undergo more complex growth than algae perhaps they're more metabolically active with regards to amination and protein synthesis?

Consider that a hydroponically grown spathiphyllum will maintain steady growth with just the ambient light from a nearby window. Presumably the protein synthesis that is supporting that growth must directly relate to the removal of nitrogen from the water. In contrast, with similar levels of ambient light it seems you wouldn't be able to grow any algae on a scrubber at all. While each photon of light may relate to a unit of waste removed, why do you need so much light to support the algae?

Well, as I diclaimed, I don't know for sure. My logic is thus :

Splitting CO2 apart requires energy.
Splitting NH3, NO2 and NO3 apart also requires energy.

The benefit to the plant from splitting those two things apart is C and N that it can tie up into biomass (yes, any biomass like stems and roots will require C and N, so any growth would be good growth.)

The only source of input energy is light, so it follows that a plant that can use more light can split more C and N products up and build more biomass. Now this is obviously grossly simplified, as different plants will have different characteristics that will affect all this - but in the absence of a mental catalog (or the desire to do the research!), that's the mode of thinking I've used. I keep hoping someone else will come up with an all encompasing explanation

 

[Noto]

Re: micronutrients

One difference here is that with plants in the aquarium, you are starting with a particular plant and trying to tailor the nutrients available in the system to its needs; with the algal scrubber, you are starting with the system and whichever algae happen to be present and letting the algae which are best suited to the system prosper. Not necessarily a general difference between algae and embryophytes, just a difference in approach.

Many algae are mixotrophic, i.e. they have heterotrophic as well as autotrophic tendencies, and so can take up dissolved organics and even organic particles unavailable to most embryophytes.

The following elements are commonly required by algae: N, P, Cl, S, Si, Na, Ca, Mg, Fe, K, Mo, Zn, Cu, Co, V, and Br/I. Of course not all algae require all of these elements. In freshwater systems the most common limiting elements are P, N, or Fe, in marine systems N or Fe.

Possibly relevant: algae can readily use ammonia/ammonium without altering it, but in order to use nitrate they must use nitrate reductase and its cofactors Fe and Co. So, these elements could conceivably affect a scrubber's ability to remove nitrate.

Does all this mean that adding iron and micronutrients to your tank will improve your scrubber's efficacy? I don't know.