Bio Balls

How about you convert that down a little so we understand what you are saying. I mean that respectfully.

 

Sure, it pretty simple, really, the tough part is getting past my explanation probably, but here's a go at it...

First, denitrifying bacteria get derive energy and grow from organic carbon, but nitrifying bacteria can derive energy and grown using inorganic carbon (which they can covert to organic forms).

There are only 3 species ("types") of inorganic carbon in our tanks, carbonate, bicarbonate and CO2. Nitrifying bacteria can often use CO2 and inorganic nitrogen, such as ammonia to derive energy. This is good, because Co2 is plentiful in our system, the levels in our tanks are basically constant and determined almost exclusively by the levels outside of the tank (give or take a bit due to gas exchange due to things like skimmers, or glass covers etc...). So, the CO2 levels equilibrate more or less instantly and there is therefore always a prevalent source of food for these bacteria, throughout the system.

Denitrifying bacteria however, needs "food" that is it needs organic carbon, plus other molecules such as oxygen to derive energy from the food. However, when oxygen becomes low, these organisms can also use nitrate in place of O2.

So, nitrifying bacteria can live anywhere and has lots of food available. There is lots of carbon and lots of inorganic nitrogen.

The denitrifying bacteria then will have lots of inorganic nitrogen, if they are in close proximity to the nitrifying bacteria. I.e. if they aren't in close proximity, they have to wait and hope a nitrate molecule passes by. If they are in close proximity though, they can gather nitrate, right from the nitrifiers, as they produce it.

This is further limited because the nitrifiers can live anywhere, but the denitrifiers can only live (or at least only reduce nitrate) in more limited (low 02) environments. So, first, if we have lots of surface area, the nitrifiers will end up all over it, but if we can limit the surface area, to areas where low and high O2 levels are in close proximity, then we can improve the probability that these bacteria will end up in close proximity (the bacteria also help this along by growing in films, where O2 permeability decreases from top to bottom, but decreases more quickly of course if O2 is lower to begin with).

So, now then, we also have the carbon issue. This as mentioned isn't an issue for the nitrifying bacteria, because CO2 is ubiquitous ("everywhere"), but the organic carbon, tends to be locked up in solids, which may or may not be soluble. In order to be useful though, these need to get to the bacteria and be in a form they can use, otherwise a limitation occurs. Carbon dosing, such as vodka or vinager dosing, provides a soluble form of organic carbon, that can quickly get to wherever it is needed. So, when carbon dosing, some carbon may be used for growth of organisms, but it is used even more, as it can also be used for energy. So, now no more bottleneck.

Carbon dosing however, isn't the only way to add carbon. Adding food will add carbon, however, it will also add nitrate and phosphate, so, any improvement in denitrification may be lost, but that may depend on the bioload and other factors such as whether or not the food is in "excess", what methods are employed to removed "excess", as well as other organisms in the system. Other organisms too will produce organic carbon though, such as macro algae, grown in a refugium, or even nuisance microalgae (although these can compete for space with bacteria). And there are ways to reduce the phosphate and other organics, independent of bacteria, such as protein skimming, GFO, GAC etc.. So, if the bioload is matched to the environment, nitrate accumulation, even without carbon dosing is not necessarily an issue. There are also organisms that produce nitrate, such as some cyanobacteria, however, these tend to feed preferentially off of sources such as urea and therefore are also highly correlated with fish waste and stocking, food etc...

So, as mentioned, I'm not saying your wrong, but I think your correct within certain specific cases, such as a tank that is pushed to the limits of its carrying capacity or a tank that simply does not promote an optimally balanced ecological system for one reason or another.

 

Two things come to mind on why a mature tank has nitrate rise faster. 1) beneficial bacteria in every nook and cranny and it is very effective at attacking ammonia and racing through the nitrogen cycle. 2) dead spots were detritus and organics build up and are decaying.

This is my layman understanding

 

When you add carbon to your tank such as in a mechanical filter does this help?

 

My resources available to me when I started with a Hand-me-down tank came with a ton of bioballs in the sump. I used it for about 1 year. I had about 60 pounds of live rock on display in a 55 gal tank. + a 20 gal sump. I noticed lots of this weird sandy silt stuff sticking to the backs of my tank and it would stick like algae but it wasnt. But it was on all the liverock. I don't know if the bioballs were the cause of this. I just know I never hand any real problems with algae.