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How much Seachem Matrix should you use?

Seachem Matrix is a biological filtration media that is designed to remove ammonia, nitrites and nitrates. So, how much of these specialized rocks should you put in your fish tank?

You can find out in this guide at Aquarium Blueprints.

What are the packaging sizes for Seachem Matrix?

The Matrix can be bought via the following packaging size options:

  • 50 mL
  • 100 mL
  • 250 mL
  • 500 mL
  • 1 L
  • 2 L
  • 4 L

How much Seachem Matrix should you use per gallon?

Officially, Seachem recommends using 5 mL of Seachem Matrix for every gallon of your fish tank.

You can find the recommended amounts for the most common aquarium sizes below:

  • 2.5 gallons = 12.5 mL
  • 5 gallons = 25 mL
  • 10 gallons = 50 mL
  • 15 gallons = 75 mL
  • 20 gallons = 100 mL
  • 25 gallons = 125 mL
  • 29 gallons = 145 mL
  • 30 gallons = 150 mL
  • 40 gallons = 200 mL
  • 50 gallons = 250 mL
  • 55 gallons = 275 mL
  • 65 gallons = 325 mL
  • 75 gallons = 375 mL
  • 90 gallons = 540 mL
  • 125 gallons = 625 mL
  • 150 gallons = 750 mL
  • 180 gallons = 900 mL

If you tank size isn’t shown above, then you simply multiple the size, in gallons, by 5 mL, to get the recommended amount.

How much Seachem Matrix should you use per liter?

If you are using liters, or litres, to measure your tank water volume, then you can use the following calculations:

  • 10 liters = 12.5 mL
  • 20 liters = 25 mL
  • 40 liters = 50 mL
  • 60 liters = 75 mL
  • 80 liters = 100 mL
  • 100 liters = 125 mL
  • 116 liters = 145 mL
  • 120 liters = 150 mL
  • 160 liters = 200 mL
  • 200 liters = 250 mL
  • 220 liters = 275 mL
  • 260 liters = 325 mL
  • 300 liters = 375 mL
  • 360 liters = 540 mL
  • 500 liters = 625 mL
  • 600 liters = 750 mL
  • 720 liters = 900 mL

If you don’t see your tank size mentioned above, then you can multiply the size of your tanks, in liters or litres, by 1.25 mL to get the recommended amount.

Can you use more Seachem Matrix than the recommended amount?

You can absolutely use more Matrix than the recommended amount by Seachem. This product is inert, which means it will not change the pH or alter any other parameters of your tank water.

The only limiting factor is space. Even if your run out of room in your filter, however, you can place Matrix directly in your tank. If you decide to use this method, we recommend placing the medias in a filter bag as doing so will make it easier to remove the pebbles and rinse them off for maintenance.

You can also use Matrix as a substrate. To find out how to do so, you can take a look at this tutorial.

How much more Seachem Matrix can you add to your aquarium?

So, how much more Seachem Matrix should you add to your fish tank? The answer depends on your water parameters.

Ideally, you should keep your nitrate levels to below 40 ppm. If you are keeping more sensitive fish and other aquatic pets, then you should keep nitrates to below 20 ppm.

The bacteria required to reduce nitrate levels can take as much as a month to start showing some results. Therefore, we suggest adding the official recommended amount to start out. If, after a month, you are still seeing high nitrates levels on your test kit, then you can start adding more Matrix pebbles to your tank.

There are other ways that you can also reduce nitrates in your aquarium. To find out how to gradually and safely reduce this compound, you can check out this guide.