There are several things I consider when deciding which media is "best". They all do the same thing, i.e. provide real estate that allows a bacterial colony to grow and live on. That's it; that's their sole function.
Some folks think the best biomedia has the greatest surface area per unit volume. But the actual surface area you will need to support enough bacteria is surprisingly small; I'd wager that about 95% of us reading this have far, far more media than absolutely required for our bioloads. And that's all you're gonna get; your tank will support as many bacteria as the ammonia production of your livestock permits. More biomedia...more real estate...does not translate to more bacteria, or better filtration. It just means that the colony will be more thinly distributed over the larger area, making it somewhat easier and more convenient to remove portions of it to start up new tanks without waiting for cycling from scratch.
Cost is near and dear to my heart; I want to get what I pay for and I don't want to pay for more than I get. Boutique high-tech biomedia grows exactly the same bacteria as cheap DIY stuff.
I want stuff that is easy to rinse clean, so that I can quickly remove any sludge or other build-up that accumulates over time. Hand in hand with this is light weight; some media that are cheap and work well also weigh a ton; other types are featherweight by comparison.
K1 is a special case, whose marketing people have sold the idea that by tumbling it you are constantly dislodging and knocking off old decrepit worn-out bacteria, allowing only the trim healthy fighting-weight bacteria to remain. Guess what? Fat old bacteria still eat ammonia. In reality, K1 has a single benefit: it looks cool as it tumbles and gyrates. If you are the type of aquarist who enjoys looking at your filter as much as looking at your fish, this is definitely your biomedium. It's the ultimate in virtue-signalling filtration media; "I love my fish so much...look how much money I spend on media!"
Pumice or lava rock is sort of a cheap version of ceramic rings or Matrix. All of them are porous and riddled with internal spaces that increase surface area. All of them will quickly have these passages and voids clogged by biofilm, negating this advantage almost entirely...but, again, you don't need anywhere near as much biomedium surface area as many sources lead you to believe, so these will continue to work just fine long after they have morphed into essentially a handful of pebbles or marbles. All can be easily rinsed off but are very heavy and inconvenient to move, and simple rinsing will not clean out all those nooks and crannies. Some folks claim that there will be anaerobic bacteria living inside the media after it clogs up which will scarf up nitrates. Hmmm...maybe...but then the anaerobic filtration gurus all state they need to "feed" their little darlings with some source of carbon, such as vodka, since the anaerobes are using the nitrates as a source of oxygen rather than nourishment, and still require some outside source of food. If that's the case...how do anaerobes living within clogged chunks of Matrix do their job? Answers to this puzzle gratefully accepted if they come from people who don't work for the manufacturers and if they also haven't bought the stuff already and need to justify the expense.
In case it hasn't become obvious by now...the "best" is a concept that is largely or completely subjective. Everybody places different emphasis on different parts of the equation. Personally, I have two "bests". The first is Poret foam, used in sponge filters or as layers in traditional sumps or other filters. This stuff lasts virtually forever, and functions as a terrific medium for either mechanical or biological filtration. As a mech medium, it can go long periods of time without clogging, so if that's the mindset that turns your crank you can stretch out the time between cleanings a bit longer. As a biomedium, it as a large amount of surface area and can be easily rinsed off to remove sludge and other clogging material without destroying all the bacteria. I've had slabs and chunks of Poret that were rinsed off many hundreds of times and remained biologically active and effective for well over a decade, and could still have continued on for far longer if required. The stuff is terrific; sadly, it's also very heavy and sloppy to handle when wet, so good mechanical prefiltration makes life easier and more pleasant when using it. It's also not cheap...but, in this case at least, you do get what you pay for.
My other choice for biomedium greatness is...plastic shotgun shell wads, sold for use in home reloading of shotshell ammunition. They look sort of like giant K1 pellets, with a surprisingly convoluted shape that increases their surface area significantly. I use them in DIY trickle filters, with a slab or two of Poret at the top to act as mechanical prefiltration media (and often changed out and rinsed daily). The shotgun wads are contained in mesh bags for ease of handling. When it is desired to rinse off the sludge, you grab the bag, pull it out of the filter, let the water drain off (takes about 5 seconds, tops) and the bag now weighs a few ounces per cubic foot; very easy to carry to the slop sink or the back yard for a quick hose-down. Like Poret...these things last forever, never break down, never lose any efficiency. They are so cheap it's scary; I have about 8 cubic feet of it in one trickle tower, total cost maybe $12...and that's twelve Canuckistani dollars, usually worth essentially nothing.
These two types of media, Poret and Remington
, have been working like gangbusters for me for probably 30 years. I've occasionally bought more as my needs expanded; I have never had to replace any or had any of it wear out or otherwise fail. That....is the "best".
Some folks think the best biomedia has the greatest surface area per unit volume. But the actual surface area you will need to support enough bacteria is surprisingly small; I'd wager that about 95% of us reading this have far, far more media than absolutely required for our bioloads. And that's all you're gonna get; your tank will support as many bacteria as the ammonia production of your livestock permits. More biomedia...more real estate...does not translate to more bacteria, or better filtration. It just means that the colony will be more thinly distributed over the larger area, making it somewhat easier and more convenient to remove portions of it to start up new tanks without waiting for cycling from scratch.
Cost is near and dear to my heart; I want to get what I pay for and I don't want to pay for more than I get. Boutique high-tech biomedia grows exactly the same bacteria as cheap DIY stuff.
I want stuff that is easy to rinse clean, so that I can quickly remove any sludge or other build-up that accumulates over time. Hand in hand with this is light weight; some media that are cheap and work well also weigh a ton; other types are featherweight by comparison.
K1 is a special case, whose marketing people have sold the idea that by tumbling it you are constantly dislodging and knocking off old decrepit worn-out bacteria, allowing only the trim healthy fighting-weight bacteria to remain. Guess what? Fat old bacteria still eat ammonia. In reality, K1 has a single benefit: it looks cool as it tumbles and gyrates. If you are the type of aquarist who enjoys looking at your filter as much as looking at your fish, this is definitely your biomedium. It's the ultimate in virtue-signalling filtration media; "I love my fish so much...look how much money I spend on media!"
Pumice or lava rock is sort of a cheap version of ceramic rings or Matrix. All of them are porous and riddled with internal spaces that increase surface area. All of them will quickly have these passages and voids clogged by biofilm, negating this advantage almost entirely...but, again, you don't need anywhere near as much biomedium surface area as many sources lead you to believe, so these will continue to work just fine long after they have morphed into essentially a handful of pebbles or marbles. All can be easily rinsed off but are very heavy and inconvenient to move, and simple rinsing will not clean out all those nooks and crannies. Some folks claim that there will be anaerobic bacteria living inside the media after it clogs up which will scarf up nitrates. Hmmm...maybe...but then the anaerobic filtration gurus all state they need to "feed" their little darlings with some source of carbon, such as vodka, since the anaerobes are using the nitrates as a source of oxygen rather than nourishment, and still require some outside source of food. If that's the case...how do anaerobes living within clogged chunks of Matrix do their job? Answers to this puzzle gratefully accepted if they come from people who don't work for the manufacturers and if they also haven't bought the stuff already and need to justify the expense.
In case it hasn't become obvious by now...the "best" is a concept that is largely or completely subjective. Everybody places different emphasis on different parts of the equation. Personally, I have two "bests". The first is Poret foam, used in sponge filters or as layers in traditional sumps or other filters. This stuff lasts virtually forever, and functions as a terrific medium for either mechanical or biological filtration. As a mech medium, it can go long periods of time without clogging, so if that's the mindset that turns your crank you can stretch out the time between cleanings a bit longer. As a biomedium, it as a large amount of surface area and can be easily rinsed off to remove sludge and other clogging material without destroying all the bacteria. I've had slabs and chunks of Poret that were rinsed off many hundreds of times and remained biologically active and effective for well over a decade, and could still have continued on for far longer if required. The stuff is terrific; sadly, it's also very heavy and sloppy to handle when wet, so good mechanical prefiltration makes life easier and more pleasant when using it. It's also not cheap...but, in this case at least, you do get what you pay for.
My other choice for biomedium greatness is...plastic shotgun shell wads, sold for use in home reloading of shotshell ammunition. They look sort of like giant K1 pellets, with a surprisingly convoluted shape that increases their surface area significantly. I use them in DIY trickle filters, with a slab or two of Poret at the top to act as mechanical prefiltration media (and often changed out and rinsed daily). The shotgun wads are contained in mesh bags for ease of handling. When it is desired to rinse off the sludge, you grab the bag, pull it out of the filter, let the water drain off (takes about 5 seconds, tops) and the bag now weighs a few ounces per cubic foot; very easy to carry to the slop sink or the back yard for a quick hose-down. Like Poret...these things last forever, never break down, never lose any efficiency. They are so cheap it's scary; I have about 8 cubic feet of it in one trickle tower, total cost maybe $12...and that's twelve Canuckistani dollars, usually worth essentially nothing.
These two types of media, Poret and Remington
, have been working like gangbusters for me for probably 30 years. I've occasionally bought more as my needs expanded; I have never had to replace any or had any of it wear out or otherwise fail. That....is the "best".
No, no no. Pumice lasts forever, does not get blocked up.
If you get an old piece of lava from a mature filter, that you believe is all clogged up, and let it dry out over weeks, and then place it in water again. It will initially float, and then over time, days or weeks, it will sink. So it is not blocked up!
Raising bags of lava about an inch off the sump floor with a porous grill stops any sludge build up.
I only rinse my pumice every two years. Whether it needs it or not.
Absolutely, pumice lasts forever...and its channels and pores are much coarser than those of ceramic, so they will take far longer to actually clog up, and are easier to rinse as they do. And the rough convoluted surface will always have enough surface area in any case.
Take a piece of Poret foam that is used for biomedia, and has become biologically active and colonized. I don't care how carefully you prefilter the water that runs through it; when you pick that piece of sponge up and give it a squeeze while rinsing, you will get coffee that you don't want to drink. That stuff is clogging the sponge as it forms; sorry, but it's going to form in pumice the same way, and is going to clog it up the same way. It's inevitable.
But taking a mature, biologically-active piece of biomedium, and then drying it out bone-dry as part of cleaning it out, runs completely countercurrent to my ideas of biomedia. I want them to become, and remain, biologically active and alive permanently...I'm certainly not about to kill off those bacteria periodically to keep the thing clean.
There's no right or wrong answer; again, it's all subjective. The ideas of the fluid-media guys are at the extreme opposite end of the spectrum from your idea about pumice...and neither of those ideas is "wrong", or "best".
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