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Is Seachem Flourish any good?

If you are planning to grow live plants in your fish tank, there may be a chance that you run out of nutrients over time. To compensate, a lot of fish keepers like to use a supplement, such as the best selling Seachem Flourish Comprehensive Supplement for the Planted Aquarium.

You can find our experience with this fertilizer in this Aquarium Blueprints review.


The Seachem Flourish Comprehensive Supplement is made up of the from the following ingredients:

  • Boric Acid
  • Calcium Chloride
  • Cobalt Sulfate
  • Copper Sulfate
  • Ferrous Gluconate
  • Manganese Sulfate
  • Magnesium Chloride
  • Magnesium Sulfate
  • Potassium Chloride
  • Protein Hydrolysates
  • Sodium Molybdate
  • Zinc Sulfate

Guaranteed Analysis

You can find the guaranteed analysis of the contents in the product below:

  • Total Nitrogen: 0.07%
  • Total Phosphate: 0.01%
  • Soluble Potash: 0.37%
  • Calcium: 0.14%
  • Magnesium: 0.11%
  • Sulfur: 0.2773%
  • Boron: 0.009%
  • Chlorine: 1.15%
  • Colbalt: 0.0004%
  • Copper: 0.0001%
  • Iron 0.32%
  • Manganese: 0.0118%
  • Molybdenum: 0.0009%
  • Sodium: 0.13%
  • Zinc: 0.0007%

Size Options

The Seachem Flourish Comprehensive Supplement comes in four different bottles: 50mL, 100mL, 250 mL and 500 mL. According to our packaging, a 500 mL bottle is good enough to treat 200 gallons of water for the course of 4 to 6 months.

Seachem Flourish Expiration Date

The expiry date can be found near the bottom of the front label of the bottle. Seachem recommends that you keep the supplement refrigerated three months after breaking the seal. The colder temperature will prevent mold and fungus from forming in the package.

Furthermore, we also recommend keeping the cap tightly closed when you are not using the product. This is because the supplement will lose its potency every time due to the exposure to oxygen.

Do your aquatic plants need fertilizers?

Plants need macro-nutrients in order to grow and maintain their health. The nutrients include boron, copper, iron, chloride, manganese, molybdenum and zinc. If there are a lack of macro-nutrients in the water column, then you plants could end up suffering from deficiencies. Below is an image created by the user known as Zapins on Aquatic Plant Central that will give you an idea as to what your aquarium plants could look like if there’s a lack of certain nutrients in your tank waters:

Image source: Aquatic Plant Central

Some of the needed nutrients could already be in your tap water or wherever you are getting your source water from. A few fish food may also include a few trace elements that your plants will happily consume.

If you want to make sure that you are getting the most important nutrients, than the best way to do so is through a dedicated supplement.


What we loved most about the Seachem Flourish Comprehensive Supplement is that it contains the aforementioned macro-nutrients. Therefore, the product takes all the guesswork out when it comes to figuring out what your water nutrients is lacking that will make it suitable for healthy aquarium plants.

In our tanks, we used the supplement to help with our Java Fern, which weren’t growing as well as we expected. Since adding the formula, the leaves look significantly better and we are seeing nice growth. The other underwater plant we have in your fish tank, Java Moss, also exploded and has taken up a majority of the tank as well. Needless to say, this product works great for us.


The only real issue we have with Seachem Flourish is that the bottle gets really dirty for us even though we made sure not that none of the solution get on the outside of the bottle. We have to wrap it in a plastic bag and place it on a coaster to prevent any of the brown substance from getting on the fridge.

The Seachem Flourish bottle can get dirty easily.

We should also mention that this product is for aquarium use only and, thus, won’t be effective on house plants. It also contains 1,5-Pentanedial and may cause an allergic reaction. If you somehow consume the solution and/or suffering from irritation after making contact, then you should seek medical assistance as soon as possible.

If you have snails and/or shrimps, then it might be important to know that Seachem Flourish includes an extremely small amount of copper, which is deadly to invertebrates. With that said, we have used the product without any noticeable issues in our tanks that are home to Assassin Snails, Bladder Snails, Ramshorn Snails and Red Cherry Shrimps. Of course, your mileage may vary. So, if you are still feeling unsure, then you are better off looking for another supplement that doesn’t contain any traces of copper.


Seachem recommends that you dose 5 mL of Flourish to treat 60 gallons of water once or twice a week. The cap that comes with the bottle will hold 5 mL. There are also threads inside the cap that you can use for smaller doses (one thread is equal to around 1 mL). You can find the dosage amount for the most common aquarium sizes below:

  • 10 Gallons = 0.8 mL (0.2 caps)
  • 20 Gallons = 1.7 mL (0.3 caps)
  • 29 Gallons = 2.4 mL (0.5 caps)
  • 40 Gallons = 3.3 mL (0.7 caps)
  • 55 Gallons = 4.6 mL (0.9 caps)
  • 75 Gallons = 6.3 mL (1.3 caps)
  • 125 Gallons = 10.4 mL (2.1 caps)

If you tank size is not on the list, you can check out the calculator on the official Seachem website (you have to click on Directions and Dosage Calculator to get access to it).

In our 55 gallon tank, we usually dose one capful once a week and have gotten great results so far. So you shouldn’t worry too much if you accidentally overdosed a little bit of the supplement. If you fear that the overdosed solution will harm your fish and/or plants, you could always do a simple water change to bring the concentration down to safer levels.

We also like to dose Seachem Flourish right after our weekly water change. This is because it is easy for us to remember and more convenient (since we are adding Seachem Prime and new water to our fish tank at the same time).


Seachem Flourish is an excellent supplement for your planted tank as it provides are the vital macro-nutrients. If you plants are not doing well, or you simply want some insurance just in case something happens, then we highly recommend this product.

If you are interested, you can purchase Seachem Flourish Comprehensive Supplement for the Planted Aquarium with this link on Amazon.