Algae Problems? Check your Nitrates!

So I was having problem keeping the chlorine levels up in my swimming pool which resulted in a layer of yellow mustard algae around the bottom and sides of my pool.  As an owner of a saltwater system, my original thought was that my salt cell either needed cleaning or replacing.  After thoroughly cleaning the cell, the issue seemed to persist.  I was reluctant to replace my salt cell because 1) I am a cheap bastard and those things are expensive and 2) I hadn’t owned this current saltwater system that long and it didn’t make sense it needed replacing this soon.

Doing some further research I discovered that I should check the nitrate/nitrite levels in my pool.  FYI, many pool stores offer this service for free.  Apparently, my nitrates were off the chart.  Or on the highest end of the test strip.  Yay me!  Being the skeptical one of pool store test strips, I began to ask a lot of questions.

Where do nitrates/nitrites come from?

Well the first thought when I hear the word nitrates is fertilizer.  And of course, one of the ways in which nitrates can enter the pool is just that.

1. Fertilizer blown in the pool, washed in from the yard, or carried in via animals/people.

One question that the lady operating the test kit asked me was if I had small children.  She asked me that because as we all know; everyone pees in the pool.

2. Urine or fecal matter carried into the pool via animals/people add nitrites.

Other potential reasons were provided (see below), but I was pretty certain the top two was sufficient enough for me.

3. Rain water during electrical rain storms.

4. Decayed vegetation, such as beans, and/or rain water run-off contaminated by nitrites.

5. Administering any product to the pool that is nitrogen based. (Ahhh.  The old catch-all)

Are nitrates/nitrites in my pool hazardous?

In short, they aren’t good for you.  Nitrates are essentially food for algae.  Nitrites are converted from nitrates (and back again in the circle of life) and when ingested, can remove oxygen from the blood.  Babies and toddlers are susceptible to having gastrointestinal problems if they swallow pool water from a pool with high nitrites.  So essentially, the pool store lady did a good job of instilling fear.

How do I remove nitrates/nitrites?

So I’m in a pool store.  The lady has insisted everyone in my family will die immediately due to my high nitrate levels, and she has a little dark pink test strip shoved in my face as proof.  Surely she will now try to sell me $100s worth of nitrate removing chemicals to save my life.


Turns out there are 4 main ways to remove nitrates and nitrites and only one viably worth doing.

  • Ion exchange (not to be confused with ionization for swimming pool sanitation)
  • Biological denitrification
  • Reverse osmosis or electrodialysis


  • Draining the pool and refilling with freshwater not contaminated with nitrates/nitrites!

No God Please No! 20062016104230Yup.  I was told to drain my pool, refill it, and come back and have it retested.  So while the lady didn’t sell me any specialized nitrate removing chemicals, she knew she was going to get me having to re-chemical my entire pool after refilling.  Well played pool store lady.  Well played.

How do I test for nitrates/nitrites?

Purchasing a simple test kit will suffice.  They have little test strips with varying shades of a color representing All-Is-Well to Evacuate Immediately.  Here is one off Amazon that should suffice.

Aquachek Nitrate / Nitrite Pool & Spa Tests Strips

Typically you should test your pool 3-4 times a year and maintain your nitrate/nitrite levels less than 10 ppm.  While I hope you never have to encounter nitrate issues, I hope this article serves you well should you encounter frequent algae problems and ineffective chlorine.