Bio Media Question

[mpeterb]

I asked this of a shop keeper who was trying to sell me some new media with some ridiculously high surface area, and it stumped him - so I'm tossing it out here.

The selling point on a lot of biological media is surface area - X has more surface area than Y, so you get better bio-filtration.

My question is, how much can that possibly matter? With no filter, and light and slow stocking, every surface in a tank will eventually grow beneficial bacteria. A filter provides you with a concentrated area and pushes the water over the bacteria better.

Once you have cycled a tank though, you only need more bacteria if something changes, and unless it's something drastic, you don't need more surface area, just time.

In brief, once you have zero ammonia and nitrites, you obviously don't need more surface area.

I'll confess I felt pretty smug following up the shop keepers sales spiel with this. Was I right?

[Diana]

In nature there are a lot less fish per gallon, so all the surfaces in a lake or river hold enough microorganisms to handle the waste load of the fish, turtles, insects, otters, hippopotami, and so on.

In an aquarium there are many many times as much waste produces per gallon, so the microorganisms need to be present in significantly larger numbers.
About the only way to achieve this is by using media that has an extremely high surface area, and sufficient pore space for the water to flow slowly through the media.

Most sponges as found in Aquaclear Power Filter, Fluval canisters, Rena Filstar Canister, Eheim canisters and many others will grow a LOT of bacteria. For larger set ups there are media for ponds that will work in aquarium sumps. Bio Wheels also hold a surprisingly large population of nitrifying bacteria.
Most of these filters will also sell you ceramic or other media that is intended to house bacteria.

If the tank is densely planted the plants will do a lot of the work of bio filtration, so you can get by with a bit less in the way of biological filter media.

The conditions in some locations in an aquarium are not always ideal for these bacteria, so while you may think there is a lot of surface area, not all of it will be swarming with microorganisms.

These microorganisms live on surfaces in a biofilm. This is a mix of protein and other materials secreted by the organisms. It is a complex web with channels for water flow. This is the slimy feeling stuff that grows on things in the water.

Nitrifying bacteria have some specific needs. The other microorganisms also have some specific (but different) needs. They will all live together quite well when all their needs are met.

~High oxygen. I have read that the nitrifying bacteria need as much if not more oxygen than the fish in the tank! This high oxygen water will not be found very deep in the substrate, only in the top layer or two of the gravel or sand. Any deeper, and there is not enough water movement to keep the substrate well enough oxygenated for nitrifying bacteria. This is the key to an Under Gravel Filter. By pulling the water through a coarse gravel the oxygen level is higher, so the bacteria can live.
~ Ammonia. No problem with this. If you have livestock, you will have ammonia. Plants prefer ammonia as a fertilizer, so in an aquarium with a lot of live plants there will be a smaller population of nitrifying bacteria.
~ Slow or moderate water flow. Too fast, and the water can blast the biofilm right off the media.
~No toxins. This means no medications, proper mineral levels, correct pH, and other things.
~ Small amount of minerals. The nitrifying bacteria need some minerals, and are tolerant of a very wide range of minerals. I am pretty sure it is the same species of bacteria in all our fresh water tanks, from soft, acidic Amazon River to hard, alkaline Rift Lakes. Different species in marine tanks, though.
~Optimum pH is in the mid 7s to mid 8s. These bacteria really slack off in the low 6s. I do not know if it is specifically the pH, or if it is the very low mineral levels that are usually associated with that low pH.
~ low light. This means that the upper surface of the substrate will not have a big population of bacteria. The bottoms of those pebbles will, though.

So... here is how it stacks up:

A good filter, well maintained, with sponges, floss and perhaps bio media such as ceramic noodles or bio wheel may hold as much as 50% of the bacteria in an aquarium system.

Fairly fine gravel or coarse sand will hold perhaps 25% of the bacteria. Coarse gravel has too little surface area, even when you count the gravel deeper down. Reasonable water flow, but just not enough surface area. The finest media such as play sand and finer does not allow good water flow. There will be bacteria only in the upper 1/8", maybe 1/4". This has a lot more surface area than the coarse gravel, even in that shallow layer.
A well planted tank is different. Plants pump oxygen into the soil, so it is reasonable to assume there will be a higher population of microorganisms deeper in the substrate.

All the other surfaces may hold 25% or so of the bacteria.
Driftwood: Has lots of pores, but I am not sure about good water flow through it.
Lava rock: Lots of surface area (especially compared to a smooth rock)Lots of shadows, even when the rock is mostly stuck up into the water.
Smooth rocks (Cobbles, river stone): Very little surface area. Often partially buried, so whatever is hidden from the light will usually grow bacteria.
Ceramic merpeople, castles and similar things: Very little surface area, and most of that is int he light. Not a good home for bio media.
Plastic plants: The finer ones will slow the water flow, and bacteria can live in the underside of the leaves, away from the light.
Live plants: These also harbor a pretty good population of microorganisms, including nitrifying species. Plants offer so many other benefits that they are really a great addition to an aquarium.

So... was the salesman stringing you along, trying to sell you large surface are products? No. There is a need for high surface area media for enough bacteria to grow.
Was he trying to push the expensive product when a less expensive would do? Probably. I use a lot of sponges in my filters, and not many of them are the expensive Bio Media sort of product.
I get mechanical and biological filtration from these sponges.

[55gal]

sorry to hijack this post but how long does it take for you bio-wheel and sponges to build up lots of bactiera?
my tank has been in it's current incarnation for about 8 months now and there is not much building up.
thanks.

[Diana]

If you do a fishless cycle it is usually complete in about 3 weeks, even if you do not add any bacteria to start it. This means that a tank with no added bacteria can grow a large enough colony to fully stock that tank. The method that I have posted here and elsewhere was originally developed to prime the tank for Rift Lake Cichlids, which are generally stocked at high levels, and all need to be added at the same time, and the tank has little or no live plants. That is a lot of bacteria!

You may not see the bacteria on the media. The first few times I clean relatively new media is seems to go back to its original color and texture, but the bacteria are there. I have used month old media to set up a new tank.

To determine how well the bacteria colonies are thriving monitor the ammonia, nitrite and nitrate of a tank with fish.
A cycled tank will be very consistent with 0 ppm ammonia, 0 ppm nitrite and a rising nitrate level. You ought to be able to do enough water changes (frequency and volume) to keep the nitrate under 20 ppm.

If you are still cycling without fish, or are keeping a quarantine tank cycled between fish they you could add a double dose of ammonia (bring the reading up to 5 ppm). A well established bacteria colony ought to be able to remove this much ammonia within 24 hours. There may be a very brief spike of nitrite the next day, then it will be gone.

If the tank is not well cycled, or something is happening to the bacteria then you will see ammonia and nitrite, and the nitrate may not rise so fast.

Optimum conditions for the nitrifying bacteria include:
These bacteria live on surfaces in a biofilm with many other microorganisms. Conditions that help all these organisms may be slightly different, but overall a well established tank means that there is a good mix of many microorganisms.
High oxygen via good water circulation through the filter and in the tank.
Ammonia From fish or from a bottle. Again, water circulation to bring the ammonia to the bacteria.
Somewhat alkaline pH, OK from about 6.5 to over 8. Under 6.5 the bacteria seem to have a hard time. I do not know if it is the acidic pH, or the low mineral level that is often associated with that low pH.
Some minerals, generally a GH and KH over 3 German degrees of hardness means there is a reasonable assortment of minerals.
No light. The nitrifying bacteria will grow on the underside of sand and gravel, in the filter, on the bottoms of the plant leaves, in the cracks of rocks and dirftwood. But not exposed to high light.
Lots of surface area. Sponge filter media is pretty good, and each filter company makes some sort of ceramic or other media. The goal is lots of surface and enough media to slow the water flow so it does not blast the bacteria off the media.
Freedom from toxins.
For example, clean the filter media in water removed from the tank, not chlorinated tap water.
Medicate fish in a quarantine tank to keep the bacteria thriving in the main tank.

[mpeterb]

I understand how high surface area products are useful if you haven't cycled and stocked your aquarium already.

I was more pointing out to the salesman that since I already had zero ammonia and nitrites, that I couldn't possibly need more bacteria, or surface area for it. I wasn't going to get those readings any lower than zero.

If you accept that, then these fancy products can't be necessary, because clearly you can get the same results without them.

That being said, I probably wasn't too clear in my first post- That the shop keep was trying to get me to replace my biomaterial of choice while parroting whatever hagen, or whatever brand this stuff was, had written in their ad.

[Diana]

You are absolutely right. There is enough living surface for the bacteria that your tank needs to handle the waste from your fish.
When you are seeing 0 ppm ammonia and nitrite, and rising nitrate, then you sure do not need to do anything else about the bacteria. You have an established system there, everything in balance.

Some reasons to add more media:
If you are intending to start a new tank, you might run its filter (new media) on the old tank for a few weeks to get a starter population of bacteria going.
This will not grow MORE bacteria than there is already, just that some will colonize the new material, and some may die off elsewhere. It is always reproducing and dying, this is natural, not a problem. When you remove the colonized filter the old tank will be short of some bacteria and the remaining bacteria will reproduce a bit faster until it has caught up.

A bare bottom tank, little or no decorations has only the filter as a home for bacteria. Make sure there is plenty of media, and be very careful cleaning it so you do not kill off too many bacteria. Adding extra media, then cleaning it in rotation, perhaps 1/3 at a time makes sense here.

If the mechanical media is not enough, and you are having to clean it too frequently. More media, perhaps a second filter can continue filtering out the debris, giving you longer between water changes.