Jump to content

Recommended Posts

I’ve been battling Black Beard Algae and Green Spot Algae for some time now. I’ve adjusted my fertilizer dosing, I have adjusted my lighting, and now I am measuring phosphates. The algae doesn’t appear to be spreading, but I am trying to balance the tank so that I don’t have more problems. 

I bought a phosphate test kit and if I am reading this right I believe I am somewhere between 2-5ppm phosphates. I understand the number should be much lower. I am starting to research how to lower my phosphates. I guess I need to test the phosphates in my tap water. 

My tank is a 75 gallon planted tank. 76 degrees, 0 ammonia and nitrite, 5 nitrate, pH 7.4 - 8. 


Link to comment
Share on other sites

The easiest way to lower phosphates is just a big water change...unless of course your tap water has an unusually high amount of phosphates, and checking it like you said, is certainly the best start. If your tap water isn't the problem, then water changes will reduce the level. How old is your tank?

  • Like 1
Link to comment
Share on other sites

@Wes L. I did test my tap and they are close. I am producing some phosphates in my tank, but I am starting with at least 1.0 phosphates out of the tap. I included a picture of my phosphates this morning (on left) and my tap (on right). I did a 20% water change yesterday. If phosphates need to be .05, I have a long way to go. But I’m not sure what my goal should be. I have Molly fry in the tank so I do feed heavy... then again I can’t raise mystery snails so I wasn’t sure if I was feeding enough. 

@AdamTill I will need to look into that further. I followed the link and saw the statement, but nothing showing how it was determined. I’ll look into it, but do you know where I could learn more?


Link to comment
Share on other sites

I wish I could find a better link, but I remember him doing tests where he intentionally overdosed phosphates by order of magnitude with no algae issues. It was as he was working on what become EI dosing. Will poke around and see if I can find something better

  • Thanks 1
Link to comment
Share on other sites

This article is a little introduction to causes of algae and Cyanobacteria in lakes. We struggle on Lake Champlain with the effects of agricultural runoff, not to mention aging municipal sewer systems when combined with massive rainfall events.


Phosphorus is the main culprit of algae and cyanobacteria blooms in our lakes. Just one pound of...


Link to comment
Share on other sites

3 hours ago, Mitch Norton said:

I will let you know what I find as well. I can’t find much on phosphates, but I’ve always read it can be connected to algae. 

It was always held up as the villain until more modern research came along. Really wish I could find that post now.

The basic principle of EI though is that everything is in excess all the time. Ergo, non toxic levels of anything aren’t what causes algae, but poor plant health is what does it (via something else being the limiting factor per 



Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...