How much LR per gallon of tank? OR

[Scooterman]

Basically Yup, thats it, the rule helps newbies because it is an easy formula but long run many variables apply here as far as what one really needs.

I don’t believe anyone was saying that rock is necessary at all. It is just one of those things like a protein skimmer or circulation pump or even lights. None of them are necessary. I too have run tanks with out any one of these things. It all comes down to what you want to accomplish in your tank and what kind of maintenance you are willing to put into it

 

[ac7av]

I have a question,
Please explain how displacing water with live rock has something to do with its denitrifying abilities? Why is more rock, less water, less effective at doing so?

 

[Scooterman]

Good question, simply put, the more surface area the more bacteria, so you get more stability. Water will hold some bacteria but the amount compared to what is on that rock is much more & they are able to process detritus faster because you have so much rock & surface area for bacteria to thrive & grow, reproduce etc (better home).

 

[jrgilles]

I have a question,
Please explain how displacing water with live rock has something to do with its denitrifying abilities? Why is more rock, less water, less effective at doing so?

I'd say for a long time more rock is more effective. Once you hit a certain amount of rock though, it would decrease due to

1. less water flow through the rocks because they are blocked. Less flow means decreased food availability for the bacteria relying on flow.

2. If you get too much bacteria, there could be a die-off due to consumption of nitrates (ie. lack of food)

3. Less food in the water and less flow could also combined lead to less nutrient going past the bacteria, so growth could slow down and lead to a decrease in bacteria population.

 

[ac7av]

Less water flow is not good? I thought this is where the anaerobic bacteria live, do to the low oxygen and low flow to reduce the nitrate in the water?

Don’t we always say that the bacteria will rise to the level of the need (cycling a tank)?

You can not get too much bacteria unless your tank is not cycled or you don’t feed consistently, is this not correct? If not then where did the bacteria come from in the first place if there was not food to support it?

Less food in the water and less flow threw the rock would not lead to a decrease in bacteria if the bacteria was populated to the system it’s in, again is this not the cycling process we all talk about when starting a tank or making any significant changes?

 

[jrgilles]

Less water flow is not good? I thought this is where the anaerobic bacteria live, do to the low oxygen and low flow to reduce the nitrate in the water?

Don’t we always say that the bacteria will rise to the level of the need (cycling a tank)?

You can not get too much bacteria unless your tank is not cycled or you don’t feed consistently, is this not correct? If not then where did the bacteria come from in the first place if there was not food to support it?

Less food in the water and less flow threw the rock would not lead to a decrease in bacteria if the bacteria was populated to the system it’s in, again is this not the cycling process we all talk about when starting a tank or making any significant changes?

Less flow could lead to oxygen deprived areas in the rock, and this would be good for anarobes, but no aerobic bacteria. You need both kinds, but from what I understand, the aerobic is more critical. You would need a balance. More flow is much better for the aerobic bacteria.

Bacteria will rise to the level of the food source they can consume, so if less water is going past them, they have less food availability, and that is what they will rise to. They don't know what the 'level needed in the tank' is. From their point of view, they multiply based on the available food for them. More flow means more food (for aerobes.) Anaerobes live deep in the rock or under the substrate, so they would rely on nutrients/waste reaching them through other means.

You can think of SPS as an example. If you had no flow in your tank, and feed a bunch of oyster eggs, even though there was food in the system, if the flow wasn't there, the SPS wouldn't be able to eat because the food wouldn't get to them. High flow is what makes the food available.

Cycling is just letting the bacteria figure out their sustainable population levels and get in balance (ie. waste from one type leads to food for another, so many kinds all have to establish their equilibrium.)

The bacteria have no 'bigger picture' that we have. They just see what food is there, and act accordingly. Flow helps get the food to them (at least the aerobic bacteria.) So if the flow is blocked, they get less food (except anaerobes, who rely on food/nutrients getting driven deep into the oxygen deprived regions of the tank.) Much tougher to control anaerobes, but I see people building compartments under the substrate where there is no flow. Which would create a good environment for them.)

Hope that makes sense. No time to edit, got to go play raquetball before work.