Algae and Nutrients

[GoPitt88]

So I have a general question. When it comes to algae, I've always assumed that keeping a low nutrient tank would stifle algae growth. I use a skimmer, run GFO, and my Hanna phosphate Checker always reads zero, and my nitrates are usually around 10 ppm or so. I feed my fish once per day. Anyway, I've read posts on here where people, when battling different types of algae, are advised that they need more nutrients, or to stop running GFO. I'm assuming it depends on the type of algae they are battling, but that doesn't make sense to me. I'm trying to wrap my arms around the concept so I can understand. Can someone explain that to me? Thanks [emoji16]

 

[Sallstrom]

From what I've seen trying to "starve" the algae by lowering the nutrients often result in pale unhappy corals and sometimes cyanobacteria(which seems to thrive in nutrient poor conditions).
My idea is to keep nutrients at a level where the corals are happy and then use a good clean up crew to graze on the different types of algae. Sooner or later the unwanted algae is outcompeted by coralline algae. Thats why you see tanks with lots of nutrients and no GHA or other unwanted algae, at least IMO

 

[GoPitt88]

Are some types of brown algae affected in the same way?

 

[Sallstrom]

Brown looking algae are often diatoms. They are very common in newly started tanks, or if you add new material to a tank(new sand or dry live rock for example).
They are grazed by many algae eaters. My favourites are Ctenochaetus tangs for grazing diatoms. If you have patience, they diatoms often go away sooner or later when other algae start to grow.

 

[cooltowncorals]

Usually that Brown biofilm is associated with not enough phosphates according to brightwell and others running ULNS usually they suggest feeding more aminos or coral foods to counter act. If it’s brown hair algae it’s just like green hair algae eating up all of your phosphates so they read undetectable but really aren’t.

Most people aim for less than 10ppm nitrate and less than .1 ppm phosphate with a more aggressive sps target of 2-5 ppm nitrate and .03-.015 phosphate but never 0 of either as both are needed by corals to grow. If they are to many availible that’s when you see browning is sps or death and excessive algae like hair algae all over.

There are some low nutrient problems like dinoflagellates which there’s a huge post in here somewhere but yes raising them is for a specific problem.