How much will high nitrate encourage algae growth?

[physicslord]

Working on a large tank:

80 gallon tank with 5 large, 4-5 inch long fish.
Phosphate tests at ~2ppm.
Nitrate tests at 50ppm.
Ammonia at 0.3 ppm.
silicates unknown - likely to be high since tap water was used as the top-off for this system.
Small bac-pac skimmer working as hard as it can.

The tank in question has excessive derbesia and other algae growth. There are many large fish. Right now I'm just concerned with inhibiting the algae growth.
I'm wondering what the most serious factor contributing to the algae growth is.

Would it be the nitrates or the phosphate?

 

[Travis L. Stevens]

Definitely. Nitrates, Phosphates, and lights are some (if not the top) of the highest single factors in algal growth. Sorry to burst any bubble of hope You can look on the back of a bottle of Miracle Grow and read the ingredients list. Some of the largest percentages are phophates and nitrates. Just thought you might like to know.

 

[physicslord]

well, at least the lighting kinda sucks ...

 

[Travis L. Stevens]

<a href=showthread.php?s=&postid=6801312#post6801312 target=_blank>Originally posted</a> by physicslord
well, at least the lighting kinda sucks ...

As in old lights?

 

[physicslord]

oh no, is that encouraging the growth too? the lights are pretty old....

 

[Amphiprion]

Well... you need nitrate, phosphate and light to encourage algae growth. IME, nitrate can be plenty high, but until a source of phosphate is added, there is hardly any algal growth. And actually the opposite is true as well. It's just that varying levels tend to encourage differing forms of algal growth--each type seems to predominate under certain conditions.

 

[Travis L. Stevens]

<a href=showthread.php?s=&postid=6801351#post6801351 target=_blank>Originally posted</a> by physicslord
oh no, is that encouraging the growth too? the lights are pretty old....

Talk about a day full of bad luck for you. But yes. After a certain amount of time (depending on the bulb type) there is a spectral shift. The wavelength on color changes more in favor of algal growth. Especially in 10K bulbs. They easily shift more towards 6700K and even 5800K in really old bulbs. Both of which support very high algal growth. Man, now I feel like I need some good news to cheer you up with. I guess you shouldn't feel that bad, I had the same thing happening. I'm still saving for my RO unit and I was running a 1.5 year old MH and just found out my tap runs at ~660 ppm, 60+ Nitrates, and trace phosphates :eek1: Amazingly enough, I have very little algal growth. I think a lot of it is how mature your tank is. A little good news is if you cut out one of the three, nitrates, phosphates, or lighting, you will most likely eliminate or severely retard the problem.