How To Culture Or Grow Phytoplankton

Phytoplankton can add an abundance of beneficial nutrients to your reef tank and help keep your livestock happy and healthy.

When we culture our own phytoplankton we know exactly how it was grown and what is in it. That makes it better than store-bought versions in my own opinion as I want to know everything in it.

A lot of companies who sell phytoplankton sell it as a mixture of several different strains which isn’t all that great. I personally want a specific type of phytoplankton strain that will best suit my own needs.

I prefer Nannochloropsis or Tetraselmis phytoplankton as it does best for me culturing and it provides my reef tank with what it needs also. My copepod culture benefits greatly from my own culture. I have tried other store-bought options and it crashed my culture. That really sucks and is a waste of money.

In this article, I am going to teach you how to culture or grow your own phytoplankton so you can use it as you need.

Why Culture Phytoplankton

There are a number of benefits to culturing your own phytoplankton and the main benefit is an unlimited supply of phytoplankton which benefits your wallet and your reef tank. Having phytoplankton available helps keep your phytoplankton dosing schedule consistent.

How To Culture Phytoplankton

Culturing phytoplankton is pretty easy and can seem intimidating but once you get the hang of the process you should be just fine. I have done this for years and if I can do it anyone can. Plus ask anyone who buys my phytoplankton it is some of the best you can get.

What You Will Need To Culture Phytoplankton

There are a number of necessary items to start your culture. Don’t be quick to jump on any kits being sold online. These are meant to save you time yes but they don’t provide the best results. If you want a culture that never crashes and provides the densest phytoplankton possible then follow my lead here and use the tools I use.

Click here to purchase your starter culture of phytoplankton.

Be sure to purchase all the needed equipment below:

  • Air Pump – This will oxygenate the water as well as keep your culture suspended in the water column and prevent settling. VERY IMPORTANT! I personally run two of the whisper pumps for my larger culture vessel.
  • Air Line – You have to have this for your air pump to provide air to your culture vessel.
  • Rigid Air Line Tubing – This is important to keep the tubing in its place not curved.
  • Culture Sample – You can purchase my starter culture sample of nano and tet phytoplankton. I recommend having both options or culturing both types of phytoplankton.
  • Marine Salt – To culture phytoplankton for your reef tank you will need marine salt. If you have your own salt that will work but you have to get the salt to 20 ppm in your vessel.
  • F2 Fertilizer – I like Guillard’s F2 because it is the cleanest and safest option for your reef tank. It is required to actually grow your phytoplankton.
  • Culture Vessel – Without a culture vessel you will not be able to grow phytoplankton. I recommend starting small and working your way up to a larger vessel like mine.
  • Isopropyl Alcohol – This is a must also as you want to clean and sanitize your culture vessel every time you use it. This will prevent germs and any other contamination from entering your vessel.
  • Aluminum Foil Sheets – This will be used to top the phytoplankton vessel. We want to prevent anything from getting out as well as evaporation which will cause problems.
  • Lighting – This is used to fuel the growth of your phytoplankton and required to culture your own phytoplankton.

I have listed above all of the products that you will need to culture your own phytoplankton. If you use the links I have provided it will take you directly to the products I personally use.

Where To Culture Phytoplankton

Most people who culture their own phytoplankton will use a closet or a shelf in their fish room dedicated to phytoplankton. It is important not to have anything near the culture vessel as it could contaminate it.

If you are doing this in a fish room then simply block the culture from being visible with cardboard or plastic wrap. This will keep any contaminants away from the culture preventing a crash.

I like to use a closet which I have dedicated to culturing phytoplankton and it has worked well for me. The culture stays at room temperature which I feel gives a better result.

How To Culture Phytoplankton Step By Step

I will be updating this post with a video showing my process for culturing and growing phytoplankton. If you need your own starter cultures you can purchase that from me here.

PRO TIP: Before you start your culture be sure to spray your vessel with rubbing alcohol to sterilize it. Do this after each use to ensure no contaminants get in your phytoplankton culture.

Step 1. You Need Saltwater

Fill your culture vessel with saltwater but leave enough room for water movement so that it does not spill out of the phytoplankton culture vessel. Be sure your saltwater salinity is about 20 ppm or 1.015 gravity. If you aren’t 100% on the money with your measurement that will not hurt anything. I try to get as close as I can without making it a huge deal.

Step 2. You Need Air

Attach your airline to your air pump to start pushing air. Be sure to include a check valve and a control valve so that you can control the airflow. If you purchased rigid airline tubing then cut the tubing to about 1 or 2 inches above the top of the vessel. Attach the soft airline tubing to the rigid tubing and turn on the air.

You should see the water move with great flow. If it is too much for your culture vessel then use the control valve to control the airflow into the phytoplankton culture vessel. Turn the controller until it is moving the water and fast but not spilling. It is best to start this process over a sink or somewhere water is ok.

Step 3. You Need Phytoplankton

Now, this is the time to purchase your phytoplankton from me or somewhere else online. I have given several resources on phytoplankton and where to purchase so choose where you want it and when you get it you will pour it in your culture vessel. Hopefully, you are reading this in preparation for culturing your phytoplankton and already have it before you started the first steps.

Step 4. You Need F2 To Grow Phytoplankton

I love the Guilliards F2 formula as it gives me the best culture possible. You want to use 2.5 ML of F2 for every 250 ML. You can double this dose but I start small and work my way up after a few days. I dose about 20ml of F2 in my culture vessel. It is a 1000ml glass container. That is 1ml per 100ml of volume.

After you have added your culture and the F2 fertilizer you need to close up your vessel. Use the aluminum sheets to form a barrier on the top. It doesn’t have to be tight and will loosen anyway due to pressure in the culture vessel. Just fit it all around the tube and outer area of the vessel to prevent anything from getting inside.

Step 5. You Need Light To Grow Phytoplankton

Phytoplankton is photosynthetic which means it uses light to get nutrients. It requires light to grow and without it, this will not work. The light I use is cheap and works great for me. I have two different lights on one vessel so that I get the best results. One is an LED grow light from Walmart and the other is an LED grow bulb from Lowes. You only need one light and if I were to pick only one then I would skip the bulb. Both links are to Amazon because I couldn’t find them on Walmart and Lowes websites.

Step 6. It Is Time To Culture Phytoplankton

After you complete steps 1 through 5 you will let your phytoplankton culture for about 7 days. If it is a light green color then you should keep it going longer and maybe consider adding another 2ml of F2 for extra fertilization. It should be ready in a week but sometimes two weeks is needed. I like slow growth because I feel the culture is much denser and from my tests, it stores longer in my refrigerator.

Step 7. Harvest Your Phytoplankton

This is the best part. I use these bottles to harvest my phytoplankton so that I can store them in my refrigerator. They are perfect for this because they come with lids and a label you can print if necessary. I just use masking tape to write the date I harvested the phytoplankton and then store them in the refrigerator.

Be sure to shake your harvested bottles of phytoplankton at least once per week. This will keep the phytoplankton from settling and dying.

Step 8. Save A Bottle Of Phytoplankton For New Cultures

Be sure to save a bottle of your own phytoplankton so that you can continue your culture when needed. All you have to do is pour the bottle into your clean culture vessel and start the process over again. I like to start it and split it into several culture vessels which provide me with the optimal amount of phytoplankton for myself and my customers.

Here is a table of F2 dosing requirements. You can double the amount of F2 but this is what I use which grows phytoplankton good for me.

Culture Vessel VolumeF2 Fertilizer Amount
How much F2 fertilizer to use in phytoplankton culture.

Here are some pictures of my own personal set up for culturing phytoplankton.

Phytoplankton Harvest
My phytoplankton harvest sitting on my 180 gallon reef tank.


Harvesting your own phytoplankton is fun and rewarding. Your reef tank will soon be colorful and happy because of your small investment which will save you hundreds of dollars per year all because you can now culture your own phytoplankton.

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