# How Much Seachem Matrix To Use?

BrandedUW
I am setting up a Fluval 306 filter for my new 36 gallon bowfront and I'm a little uncertain about how much Seachem Matrix to use. It says to use 2L (or 2000 ml) per 400 gallons, which comes out to 5ml per gallon. So if my math is correct, that means I would use 180 ml in a 36 gallon, which is only about 3/4 of a cup. It seem so odd to be using a liquid type measurement for something like this, as I've seen many people referring to bio media in terms of weight. 3/4 of a cup is hardly any and I have tons more room than that, so should I just fill up the trays I want it in and call it a day and feel good about using extra? Or am I missing something and screwing up my calculations somehow. I have plenty of Matrix I could use, but want to make sure I'm using enough, so if someone has a different formula they use for a minimum amount, I'd love to hear it. I'm planning to use Matrix as my primary bio-media (no ceramic rings or biohome). Thanks

Cichlidude
Check out this video here.

Need about 1 kilo per 100 liters of water. Or about 2 lbs per 25 gallons.

A 2L bottle of Matrix is equal to 1.7 lbs.

BrandedUW
Hmm. At first I thought there's no way I could get that in my filter, but then I plopped my 2L container on my postal scale and it weighs 3.2 lbs. Now I know this includes the actual plastic container, but it can't weigh more than an oz or so. I'll see how much I can get in there but I should be close to the 2.88 lbs I would need with 2 lbs/25 gallons I think. Thanks

Cichlidude
Hmm. At first I thought there's no way I could get that in my filter, but then I plopped my 2L container on my postal scale and it weighs 3.2 lbs. Now I know this includes the actual plastic container, but it can't weigh more than an oz or so. I'll see how much I can get in there but I should be close to the 2.88 lbs I would need with 2 lbs/25 gallons I think. Thanks
My 2L bottle of Matrix says on the label, 1.7 lbs. What does yours say?

86 ssinit
Great video. I think your 306 has 3 chambers. Me I would make the first(lowest in canister) a corse than a fine sponge. Than the other 2 I would fill with bio media (matrix,biohome,pot scubbers...). I would also put a sponge over the intake. Clean that sponge weekly and let the rest of the canister grow for about 2 maybe 3 months or when you notice a big reduction in water flow.
Also a would recommend a second filter hob that you clean weekly.

BrandedUW
My 2L bottle of Matrix says on the label, 1.7 lbs. What does yours say?
Weird. Mine says 1.7 lbs as well, but it weighs almost twice that.
Great video. I think your 306 has 3 chambers. Me I would make the first(lowest in canister) a corse than a fine sponge. Than the other 2 I would fill with bio media (matrix,biohome,pot scubbers...). I would also put a sponge over the intake. Clean that sponge weekly and let the rest of the canister grow for about 2 maybe 3 months or when you notice a big reduction in water flow.
Also a would recommend a second filter hob that you clean weekly.
Thanks. That's basically what my plan is. I have put biofoam in the bottom tray and I was going to fill the other two with matrix, plus a thin layer of poly fill under the matrix in the middle tray and some polishing sponge material under the matrix in the top tray. Plus I have the side sponges of course. I am definitely going to us an intake sponge as well (love those). I thought about going with biohome but it's so dang expensive! I'm not sure if I'll use a HOB as well, but I am going to use a double sponge filter (which will also serve as seeding material for quarantine).

I can only get 1 lb of matrix per tray, so I guess I'll only be using 2 lbs of it since I can't take anything else out (I've already decided to forgo carbon) . It's still way more than Seachem recommends. I will also have live plants, driftwood, rocks, and sand for BB to live on, plus all the sponge filters. Hopefully that will work.

DarkOne
I just got a 2nd 306. I have the biofoam in the bottom tray with a bonded filter pad cut to fit on top. Then I have bio media in the top 2 trays. I have a 206 and 406 and they're set up the same way.

Just fill the trays with Matrix but make sure the trays stack properly. They should interlock or you'll have a lot of by-pass. Ignore the "x per gallon" instructions. Just put as much as you can in the trays and you'll be fine.

All your mechanical filtering should be done before the bio media.

Cichlidude
Weird. Mine says 1.7 lbs as well, but it weighs almost twice that.

Hummm that is interesting with your scale. No offense but are you sure because then there is misprint on the label.

aae0130
I looked at the Seachem websight and it states 250ml for 50 US gallons. I was curious about this myself because I recently picked up a SeaChem Tidal 110 and it came with 500ml of Matrix. My tank is 46 gallons so I guess it is more than enough.

86 ssinit
Yes sponge filter is also good. Only thing with the poly fill and the polishing sponge is they will slow down the flow. I’d use the poly fill where you said but remove the polishing sponge. Better flow rate.

Stoka
Check out this video here.

Need about 1 kilo per 100 liters of water. Or about 2 lbs per 25 gallons.

A 2L bottle of Matrix is equal to 1.7 lbs.
Great video. Before I had a planted tank this is exactly how I setup my Sunsun 404, except I used Matrix. Nobody would believe I had almost zero nitrates in a heavily stocked tank. Anyone serious about fish keeping should watch this.

BrandedUW
Hummm that is interesting with your scale. No offense but are you sure because then there is misprint on the label.
Yep, I'm sure. Seems weird to me as well. I almost wonder if that's supposed to be the weight that's printed on the one liter bottle. I sell books for a living and ship them all over the world so I use this postal scale every single day. Also it just feels heavier than that. I would expect it to be a little bit different but almost double seems like it's got to be a misprint.

Yes sponge filter is also good. Only thing with the poly fill and the polishing sponge is they will slow down the flow. I’d use the poly fill where you said but remove the polishing sponge. Better flow rate.
Thanks, I will consider that. It's kind of a DIY polishing sponge from a big sheet that I bought and cut. It's pretty thin so I folded it over for a double thickness. If it seems to affect the flow too much then I will either cut it in half so it's only one thickness of it or take it out all together. I have watched so many canister filter videos at this point, including the one that was posted here on this thread (though I forgot it included specific measurement recommendations like that), and tried to glean something from them all. I've got to try to squeeze some seeding material into there as well, so I guess I won't be totally filling the second two trays with matrix right off the bat, but will eventually get there.

Cichlidude
Yep, I'm sure. Seems weird to me as well. I almost wonder if that's supposed to be the weight that's printed on the one liter bottle. I sell books for a living and ship them all over the world so I use this postal scale every single day. Also it just feels heavier than that. I would expect it to be a little bit different but almost double seems like it's got to be a misprint.

Won't be the first time Seachem has been wrong. I found 4 mistakes on their web site that has been up for over 3 years and nobody knew about it. They actually fixed them the same day.

I sent an email asking what the weight is. I will call tomorrow and talk with them.

BrandedUW
Won't be the first time Seachem has been wrong. I found 4 mistakes on their web site that has been up for over 3 years and nobody knew about it. They actually fixed them the same day.

I sent an email asking what the weight is. I will call tomorrow and talk with them.
Nice. You are very proactive. Would love to hear what they have to say about this. Kind of funny since you would usually expect them to overestimate, rather than under report.

Islandvic
I wouldn't get to caught up as to what Seachem recommends for the amount of Matrix per volume of tank.

Just load the canister with as much Matrix as you can in the top and middle trays.

Having the PolyFill and polishing pads under the matrix is a great idea.

The sponge pre-filter on the intake you mentioned is a bonus.

Cichlidude, we may have to buy some random 2l Matrix bottles, weigh them, report the results and return them.

You may be having to call your friends you made over at Seachem again do they can make some updates!

I

BrandedUW
I wouldn't get to caught up as to what Seachem recommends for the amount of Matrix per volume of tank.

Just load the canister with as much Matrix as you can in the top and middle trays.

Having the PolyFill and polishing pads under the matrix is a great idea.

The sponge pre-filter on the intake you mentioned is a bonus.

Cichlidude, we may have to buy some random 2l Matrix bottles, weigh them, report the results and return them.

You may be having to call your friends you made over at Seachem again do they can make some updates!

I
I could just take my scale with me to the LFS. That wouldn't be weird at all.

86 ssinit
If you don’t have enough matrix use plastic pot scrubbers to fill in the empty space. Use the scrubbers in the second tray. Bb grows on the scrubbers

Wraithen
If you don’t have enough matrix use plastic pot scrubbers to fill in the empty space. Use the scrubbers in the second tray. Bb grows on the scrubbers
Anaerobic doesn't. The benefit of matrix the the good places for anaerobic to grow.

86 ssinit
Anaerobic doesn't. The benefit of matrix the the good places for anaerobic to grow.
Ok that’s debatable but I’m no scientist. Anaerobic bacteria grow in low oxygen and dark places. Now the pot scrubbers are dense so like matrix the interior may be able to grow ab. But I just said it would grow bb anyway . They’re cheap and do work.

Cichlidude

Hello,

Thank you for your email. Please keep in mind that since Matrix is a 100% naturally mined product the bulk density of the product will vary from each batch. This will be based on several factors including porosity of each granule and moisture content. We base our measurements on a volumetric scale for all of our chemical and biological medias for this reason. For your reference the weight we state on the bottle is:

1L = Net weight 400g (about .9 lbs)

We state the minimum net weight for the volume on the bottle, so if it is above that, it is within our parameters.

I hope this helps!

Thank you,

Seachem Support 10286
**************
So a 2L bottle would be about 1.8lbs and says 1.7lbs.

I called Seachem and talked a good half hour about this. They are now going to actually weigh a 2L bottle and get back with me. The problem is we are talking volume vs. weight.

Which weighs more? A ton of feathers or a ton of steel? Which has more volume?

Stay tuned...

Wraithen
I take a bit of issue with their reasoning. Less dense is more porous, which would be beneficial, not detrimental. So saying there is extra weight per the volume concerns me.

I really wanna see the mine they have. Are there giant "SEACHEM" signs all over the side of a volcano? Lol

Cichlidude
Ok that’s debatable but I’m no scientist. Anaerobic bacteria grow in low oxygen and dark places. Now the pot scrubbers are dense so like matrix the interior may be able to grow ab. But I just said it would grow bb anyway . They’re cheap and do work.
Pot scrubbers are not dense at all. Heck, you can see through them. They will do nothing for anaerobic bacteria. Aerobic yes, anaerobic no.

Stoka
Pot scrubbers are not dense at all. Heck, you can see through them. They will do nothing for anaerobic bacteria. Aerobic yes, anaerobic no.
Anaerobic denitrification generally takes place in the deepest places of porous media with very low flow rate. Scrubbies are good for aerobic nitrifying bacteria but useless for denitrifying bacteria.

86 ssinit
Ok what I don’t understand is the reason to want denitrifying bacteria. Unless your tank is producing more than 40ppm of nitrate between water changes you have nothing to worry about. Also as soon as you clean that canister filter you will add air and light to the media. Killing a major percentage of that bacteria. So you start over.
I guess it’s a bonus if it’s growing in my filters. But I’m not trying to grow it. No need for it. If your tank is producing 40ppm nitrates between wc you have another problem.

Stoka
Ok what I don’t understand is the reason to want denitrifying bacteria. Unless your tank is producing more than 40ppm of nitrate between water changes you have nothing to worry about. Also as soon as you clean that canister filter you will add air and light to the media. Killing a major percentage of that bacteria. So you start over.
I guess it’s a bonus if it’s growing in my filters. But I’m not trying to grow it. No need for it. If your tank is producing 40ppm nitrates between wc you have another problem.
There are advantages to having close to zero nitrates. For shrimp keeping and certain fish they are almost essential. I personally like to keep my fish in as close to optimum conditions as possible. Opening the canister will not affect in any way the denitrifying bacteria in the interior pores of your media. Just a personal preference I guess.

Wraithen
Using nitrates as a need for water changes is not such a good thing. Why change water more than once a month if the only reason is because of nitrates? Weekly and twice a month are used a lot, but that's because of nitrates usually. I change 100 to 120 gallons a month. That's 1 single water change per month. There are plenty of tanks that run for a few months with stable parameters before tds indicates a need for a water change. Doing weekly water changes because you don't know when you need to do water changes, or because you're nitrates are climbing too high, seems like an archaic way of doing things for me now.

DarkOne
Ok what I don’t understand is the reason to want denitrifying bacteria. Unless your tank is producing more than 40ppm of nitrate between water changes you have nothing to worry about. Also as soon as you clean that canister filter you will add air and light to the media. Killing a major percentage of that bacteria. So you start over.
I guess it’s a bonus if it’s growing in my filters. But I’m not trying to grow it. No need for it. If your tank is producing 40ppm nitrates between wc you have another problem.
In nature, nitrates are very rare because of denitrifying bacteria. In the aquarium, we get rid of nitrates by water changes but having 0 nitrates is ideal. Most aquarium fish can handle 80-120ppm nitrates but that's like saying you can survive a room full of cigarette smoke. Keeping as low as possible should be the goal and why some people use live plants as well as water changes to control the amount of nitrates in a tank.

The bacteria grows inside the media and isn't exposed to O2 or light during filter cleaning.

Islandvic
88ssinit, a reduction of nitrates is better for the fish's health and requires less frequent water changes.

A fish tank is actually not "fully cycled" until denitrification bacteria colonizes and reduces nitrates.

In most tanks, this usually does not occur.

BrandedUW
Who knew this question would evoke such a debate. Haha. So to continue this conversation, would a tank be considered fully cycled or at least "good enough" if nitrates are reduced by plants rather than bacteria? Or how would you tell the difference? Or does it even matter if nitrates stay low and ammonia & nitrites are 0? I keep hearing all this talk about wanting more bio media capacity in filters, but if the numbers are good, then shouldn't it be fine? Or is more always better. Just kinda thinking about this from a more hypothetical standpoint here.

Wraithen
Its a full cycle whenever the nitrates are removed from the tank without a water change. Whether plants do it or bacteria, the cycle is still a cycle in that the nitrogen introduced has left the water column.

86 ssinit
Who knew this question would evoke such a debate. Haha. So to continue this conversation, would a tank be considered fully cycled or at least "good enough" if nitrates are reduced by plants rather than bacteria? Or how would you tell the difference? Or does it even matter if nitrates stay low and ammonia & nitrites are 0? I keep hearing all this talk about wanting more bio media capacity in filters, but if the numbers are good, then shouldn't it be fine? Or is more always better. Just kinda thinking about this from a more hypothetical standpoint here.
Good question. If you have enough media in your tank that the bacteria is eating the ammonia and the nitrite and all you have is nitrate than you have enough media. As stated already its going to take a little longer for the media to reduce the nitrates. That’s why most don’t worry about nitrates (unless they go over 40ppm then we do a wc).
Your bacteria will only grow to the bio-load of the tank. So it pays to have more in case your thinking of adding more fish later.
As to nitrate if you read most of the threads on planted tanks. The fishlore pros say nitrate is good in a planted tank. Plants eat it. .

Wraithen
Good question. If you have enough media in your tank that the bacteria is eating the ammonia and the nitrite and all you have is nitrate than you have enough media. As stated already its going to take a little longer for the media to reduce the nitrates. That’s why most don’t worry about nitrates (unless they go over 40ppm then we do a wc).
Your bacteria will only grow to the bio-load of the tank. So it pays to have more in case your thinking of adding more fish later.
As to nitrate if you read most of the threads on planted tanks. The fishlore pros say nitrate is good in a planted tank. Plants eat it. .
Except with most dirted tanks and a lot of the specialty substrates the bacteria convert nitrates so we have to add it back in. I would rather do that than have to change water just because nitrates get high.

86 ssinit
Lol I’m old school and half the fun is changing water.

Wraithen
Its less fun with a large tank

86 ssinit
Yes but large tanks are much different. They are easier to keep. Had a 200 planted with a wet/dry and changed the water monthly. Have planted 15,30 and 90 and they take a little more time to keep up. I belive the hardest tank to keep up is the 10 gal. Small amount of water and can go off in a heartbeat.

DarkOne
My 75 gallon is the easiest to keep. Water changes are easy as I have a system to drain and fill w/o lifting a bucket ever. The filters are cleaned every 2-3 months (FX4 and 406). My water change system works ok with the 40 gallon and some of the 20 gallon but I find it easier to use buckets with the other 20 gallon and smaller tanks but takes more effort.

Homeslice
Pot scrubbers are not dense at all. Heck, you can see through them. They will do nothing for anaerobic bacteria. Aerobic yes, anaerobic no.

Well, if you look at one pot scrubbie on its own, that is almost certainly correct. But if you have a filter with a slow water flow and a LOT of pot scrubbies, where the water has to flow through one after another at a very slow rate, before finally leaving the filter, can't the nitrifying bacteria in the first many pot scrubbies get rid of the oxygen, so that denitrifying bacteria ending in the last of the scrubbies can get rid of nitrates due to the lack of oxygen in the water by then? This seems to be the principle on what a denitrifying reactor is based. Thanks!

Cichlidude
Well, if you look at one pot scrubbie on its own, that is almost certainly correct. But if you have a filter with a slow water flow and a LOT of pot scrubbies, where the water has to flow through one after another at a very slow rate, before finally leaving the filter, can't the nitrifying bacteria in the first many pot scrubbies get rid of the oxygen, so that denitrifying bacteria ending in the last of the scrubbies can get rid of nitrates due to the lack of oxygen in the water by then? This seems to be the principle on what a denitrifying reactor is based. Thanks!
Probably not. Still too much water flowing through a lot of holes.

aae0130
I believe the media required to accomplish this would be more like dense pumice. It you watch the videos on the subject you will see the media has large pour structure on the outside and more dense structure on the inside. Scrubbies are not going to do that. Water will blow through them too quickly. The best way to check is to try it. I wouldn’t go for that as a first option myself because if it doesn't work you have wasted 8 or 9 weeks then you need to start over.
I set up a big hob with Matrix so it isn’t any extra work for me to try it. I have the flow slowed a bit and I’m adding a prefilter sponge also.

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