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I am not a expert on blue-green algae but I do have some in a tank that had a lot of dissolved organic carbon (DOC) in it from plants rotting. I was also getting an organic scum on the surface. I removed the decay, and vacuum the soil once a week, added a bunch of E. berteroi, and fertilize per Tom Barr.

I see the cleaning you are doing is good, but I wonder about using 4 Watts/gal PC on the tank with slow growng plants. It sounds like you are trying to starve the algae. I have never heard of not fertilizing a high light planted tank without a soil substrate. I would think, as is true for most other algaes, that you will certainly kill all the plants before the algae dies.

I would certainly consider going to 2 W/g by turning off one of the 96W bulbs. Other than fertilizing and adding fast growing plants I'm not sure what would work. I think there are several other threads on blue-green algae that mention blackouts and H2O2, but I think they are for normally fertilized tanks. I assume you've read those threads.

If your PO4 is less than 4 ppm you should use the tap water. You also need a KH of 4, GH of 4 (preferably higher).

Good luck; I am interested how you beat this one, as I could use the info myself.

Steve Pituch
 

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I have never seen an explanation for the basis of the Redfield ratio or buddy ratio except somebody tried it and it worked for them. I am fighting blue-green (cyano) algae in one of my tanks by adding more PO4, and its working.

Steve Pituch
 

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No, I am adding 10 ppm NO3 and 2 ppm PO4 (5:1), twice per week with a 50% weekly water change. That's supposed to increase the cyano problem, but with weekly removal, water changes, lots of plants, and heavy fertilization, its going away along with the brown algae I had with it. I've even tried 4 ppm PO4 with no adverse effects.

I was trying to grow Wild Rice in 1/2 of my 125 gal tank for a biotope experiment, but I was getting a lot of DOC in the water and surface scum. Most of the Rice was not growing well and the decay of some of the rice plants I think was causing it. At one point I had about a 1/8 inch thick carpet of brown (diatom) algae over the whole bottom of the tank.

I got rid of the rice and starting vacuuming the tank once a week. The tank looks great at at this point and 95% of the cyano and diatom algae is gone.

Tom Barr is right. I didn't believe it the first time he told me to try not to limit PO4, but having an excess of P, N, K, or Fe does not hurt the tank. (Having one of them absent is probably a big problem). I just can't afford the good test kits to keep the ratios of these 4 elements constant in the water, and also I don't have the time. I think at this point in time the best in the state of the art for the hobby is T.B.s Estimative Index.

If someone can give us a scientific explanation for the Redfield or buddy ratio, fine, but I don't think I could ever make it work. Having a specific concentration of nutrients in the water has nothing to do with a plants capacity to take those nutrients in (including algae). I've heard of % ratios of these elements in plants and animals but again I don't think it has anything to do with how a plant will suck in those nutrients.

Regards,
Steve Pituch
 

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Walstad uses a soil substrate and fish food for fertilizer. She never uses more than 2W/g, and doesn't inject CO2. The carbon is from the decaying matter in the tank. CO2 must be conserved so she covers her tanks and does not agitate the water. The longer between water changes the better. The biological activities in the tank are going on at a normal rate. It works. You can't grow everything but you can grow quite a lot.

If you add CO2 and ton of light you will need to add more nutrients because the metabolism of the plants is greater. The aquascaper generally wants to grow the plants as quickly as possible so they are adjusting all the inputs: CO2, light, nutrients for maximum growth (maximum potential growth for algae too).

I am more of a biotoper than an aquascaper. I like to play with growing different plants, and am not concerned as much with aquascaping. So I have used both methods. You should always have at least one Walstad type of tank. It is a more natural way of keeping plants. I won 1st place in the biotope category in the AGA contest a few years ago with a Walstad tank, so anything is possible. Just remember to enjoy the hobby.

Steve Pituch
 

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Dear C_perugiae,

I don't know about eco complete but most special plant substrates you can buy help a little with iron, but thats it as far as nutrients go.

You can go two ways:

Test kit way:
Buy some really good test kits ($200-$300) worth, LaMotte, Hach), and maintain 10 ppm NO3, 1-2 ppm PO4, and 1-2 ppm Fe with traces added. You wil have to test every day until you see the trend in the tank. There should be plenty of K in the tank from KNO3.

Tom Barr's Estimative Index:
Add 10 ppm NO3, 1-2 ppm PO4, and 1-2 ppm Fe with traces twice per week. Do one 50% water change once per week. Test kits are optional. Per the math, the 50% water change limits the max of what you put into the tank to twice the weekly amount. So asuming the plants won't take in any of the nutrients (they will, you just don't know how much) the maximum concentration in your tank will be 40 ppm NO3, 2-4 ppm PO4, and 2-4 ppm Fe and traces. These are the max that can occur in your tank, but since the plants will absorb some of this the actuall ppms for each nutrient will be less. These maximum amounts are OK. So what you are doing is providng the plants with more than enough nutrients to grow without over doing it. These excess amounts will not produce algae. What you are doing is providing nutrients for your plants without using test kits.

I would order chemicals from Greg Watson's web site (very cheap): 1 # of KH2PO4, KNO3, and CSM+B.

If use use Flourish for the iron be sure to put 1-2 PPM in the tank! There is .39% iron in Flourish. Do not follow the instructions on the bottle, otherwise your plants will not have enough iron. Florish does not have NO3, or PO4.

Regards,
Steve Pituch
 

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Peter has good advice for a low light tank. In order for it to work the substrate needs to be an established one if it is going to be a substitute for a soil substrate..... but it will work. You will probably need to feed extra food, more than the fish need, to supply the plants with what they need. If you go this route you really should buy Diana Walstad's book, Ecology of the Planted Aquarium. It will be very helpful.

http://www.aquatic-gardeners.org/bookstore.html

Regards,
Steve Pituch
 
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