Algae scrubber in a mixed planted fresh water aquarium

[kramer102]

I'm interested in using an algae scrubber to supplement filtration provided by freshwater aquatic plants and eliminate water changes. I'm planning to add C02. I understand that algae and plants use the same resources . I'm assuming a few things. 1) Plants typically do not use enough fish waste to keep nitrate levels close to zero and typically need water changes for that reason. 2) Algae consumes ammonia more readily than most other plants. I've heard plants don't thrive on ammonia(too harsh) and feed better on nitrite/nitrate. 3) Algae responds much quicker to spikes in ammonia/nitrite creating a buffer in case of fish death or accidental overfeeding. 4) The plants will receive a large portion of their nutrient needs from the substrate/root system. (Although, I am curious about the long-term replenishing of nutrients to the soil) Are these close to correct?

So I'm going for a balance and therefore I do not see the typical rules of thumb working. Do we know the relationships between the three independent variables of light intensity, area, and flow versus filtering capacity? I've noticed that the general rules of thumb are assumed to perform linearly for larger and larger tanks. Any Ideas of how to easily change the filtering capacity of the ATS to allow for empirical testing? Would you change lighting, flow, or surface area?

I have not seen any examples of a planted freshwater tank with fish using an algae scrubber. So maybe this is a fools errand, but I'd like to see for myself. Any Ideas for how to calculate typical nutrient production from fish/ excess food minus nutrient absorption from plants. I'd like to make an educated guess about the size of the ATS to zero the equation.

Thanks for the help

[SantaMonica]

You have it correct mostly. Plant growth is measured in inches per week, whereas algae growth is measured in doublings per day. Plus, all of the algae is touching the water, and therefore all of the algae is in a position to do the filtering. Lastly, algae feed your water too, by adding vitamins, amino acids, and sugars (carbon), which non-algae aquarium people (especially reef keepers) buy and dose manually.

I guess you did not see them, but many planted tanks are using scrubbers. You just can't tell from the success posts, or the example pics, because either they did not specify it was FW or Planted, or they did and I forgot to carry that info over when I edited them. I'd say there are a few hundred of them on my threads alone, and a few thousand total.

Do we know the relationships between the three independent variables of light intensity, area, and flow versus filtering capacity?

Yes. The new rule for this is:

Each cube of frozen food you feed per day needs 12 square inches of screen (3 X 4),
with a light on both sides totaling 12 watts.

If you feed flake, feeder fish, or anything else, you will need to blend it up super thick, strain out the excess water, pour it into a cube, and see how many cubes it is. As for varying the strength of the scrubber (so as to not kill the plants), you would probably most easily reduce the hours of the lighting. Could even do it with a controller.

So what you would do is build a scrubber as if you had no plants. Then let it run full power until nuisance algae in the tank disappeared. Then watch to see if the plants become affected next. You many not even have to, but you could then scale back the photoperiod of the scrubber if the plants start getting weak. Although you may think you built a strong scrubber, if it's your first one, you may not have built it as strong as you hoped for, and therefore you would not need to reduce the lighting.

[inkidu]

The plants will receive a large portion of their nutrient needs from the substrate/root system.

I think some plants tend to get their food from the water while others from the soil all matters what plants you are trying to grow.

IMO If you use an algae scrubber(therefore supplying the most advantageous place for algae to grow) in a planted FW tank then you would have less of a

likely hood of having unsightly algae growing on the leaves of your display tank plants.

To put a another way say you had some algae growth in the FW planted tank that would be troublesome to remove physically you could cut the lights in the

display tank (for some period of time) and let the algae scrubber take up the nutrients that the display tank algae would "give off". Assuming the display

tank plants were already established they could take the loss of light without to much harm before the algae could.

Hope this helps.

[kramer102]

Sounds great. Thanks for the advise. Looking forward to giving it a try.

[noledoc]

Excellent questions. I'm starting a new thread that builds on this. I'd appreciate your thinking.

[durbs fw]

Hi,
I am new to this board although I have built a scrubber using the advice found here. I found that the scrubber in a fresh water system quickly uses up the phosphates leaving excess nitrates. the ratio of uptake is about 7 nitrates to 1 phosphate. After supplimenting the tank with 1 ppm of phosphates the growth on the screen was lush and green. Once the growth reduces I will add another ppm of phosphstes to observe the effects.

I felt that it was important to note that phosphates need to be supplimented in a fresh water system.

[nidayede]

The plants will receive a large portion of their nutrient needs from the substrate/root system.

[Floyd R Turbo]

I guess I have to read more SM threads. I don't remember seeing one running on a FW planted tank, I thought it was a no-no. That's awesome!

Also I would like to know exactly what the uptake ratio of N to P is. I've heard 14 N : 1 P but not durbs fw says 7 : 1. Is it different for SW reef vs FW vs FW planted?

[iggy]

You can find N:P:K ratio roughly by looking up sears collins poor mans dosing drops. Dupla used to make a recipe for growing FW plants that was deformulated.

One of the great aspects of FW planted tanls is the simplicity of the filter. I had great success eventually without ATS on then, just had a mechanical skimmer filter.

One trick I used was java moss directly on all displays that was exported to trash can. It is great at limiting P atleast initially. Potassium depletion is very real in planted tanks as well as phosphorous. It is spiked when plants show symptoms.