Media Question


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Currently working on my 225 Gallon Tank and wondering if I have enough media in my sump for beneficial bacteria to grow.

Currently it's just a planted tank, but will eventually house about 100+ Tetras.

Not including the floss and foam it currently has:

2L of Seachem Matrix Media
2750 Grams of EheI'm Ceramic Balls
150 Pieces of Bio Balls

Is that enough for the future or should I purchase more.

Also 2 other questions.

1) Can I let the Bio Balls just float on top of the Sump or better to have them on the floor of the Sump?

2) Eventually when the tank is cycled, what is a good amount of fish to introduce at a time to assure the bacteria is not overwhelmed?

Thank you! Sorry for the long post.


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5 to 10 years
When you say "EheI'm Ceramic Balls", do you mean Substrat Pro?

Bio balls are intended for use in a moving bed. If you don't have a moving bed in your sump, you're wasting space with bio balls. Plastic isn't a particularly good medium for bacteria to grow on. It's only useful in the moving bed because the weaker bacteria constantly get stripped off by the colliding balls, so you end up with very strong bacteria that can process more waste than the weaker siblings that got washed away. At least that's the theory I've heard. If it's just sitting there not moving, you're much better off using the space for something else.

As to the proper quantities, it depends on what you're trying to accomplish. Most people set up filters with the idea of converting ammonia to nitrite and then nitrite to nitrate. They assume the nitrate can only be removed via water changes. If this is your goal and you believe Seachem's reports on the biologically active surface area of Matrix, then you've probably got enough.

If your goal is to also create anoxic zones within the media to get rid of the nitrate as well, then that's a different situation. Seachem makes claims about Matrix in regard to denitrification (converting nitrates to nitrogen gas) but to my knowledge has not made recommendations on how much Matrix you need to accomplish this. The amount per gallon they do recommend is far too low to do much in the way of denitrification, so the community is left to fend for itself in regards to how much is needed. I don't have the answer.

Substrat Pro is a sintered glass media not entirely dissimilar from Biohome Ultimate. Biohome does make recommendations for denitrification. At the stocking level you're talking about you'd want 1kg per 100 liters of water. You'll have on the order of 800 liters, so you'd want 8kg of Biohome. If we assume Substrat Pro would be used at the same rate, then you'd want quite a bit more than you currently have if you want to do denitrification.

(Matrix is a natural pumice, completely different than Biohome, so I don't think the same usage recommendations would apply.)

If you're looking for other alternatives, you might want to check out the Poret-aqua media available at Swiss Tropicals. It's small foam cubes that can be used like bio balls in a moving bed or simply dumped in a section of the sump. The gaps between the cubes allow a lot of the water to flow over the outside of the cubes where aerobic bacteria grow, but the water isn't forced through the cubes, so anoxic zones can be established in the interior. I honestly don't know how the effectiveness of this media compares to Substrat Pro or Biohome Ultimate. I only mention it because it's way cheaper than most of the alternatives. If you email the owner at Swiss Tropicals and describe what you want to do I'm sure he can make some recommendations on quantity.

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