But now that you have more water vomume, the whole system gains nutrients slower and is controlled easier by the skimmer and the inhabitants are happier.

only if the skimmer is large enough to keep up

But now that you have more water vomume, the whole system gains nutrients slower

How? You didn't remove any animals, you didn't reduce feeding. The import of waste is exactly the same as before.

and is controlled easier by the skimmer

How? The output of the skimmer per unit time, is inversely proportional to the concentration of waste in the water.

If it was large enough to keep up before, and you havent added more stock, it will still pull the same but at a different rate. The water will still be more diluted.

Look at it this way.

a 20,000 litre aquarium with the same amount of livestock as someone with a heavily stocked 1000 litre system. (in other words, one little corner stocked).

The inhabitants would NEVER see nitrate or phosphate and you could still use the same skimmer. The skimmer only needs to pull out the waste from the inhabitnats, NOT the water itself.

Dilution, dilution, dilution.

That is how the OCEAN works.

however over time the tank would get polluted as the nutrients would build up. good for short term however problems long terms.

Dunno about that,

It would take months, and if you were doing normal water changes, I dont think it would.

If it did, ONE 50 % WC would refresh it for another year!

yes sure if you did water changes then it would be ok,

forgot what we are going on about anyway

well im out, makes sense both ways you look at it

Good battle, enjoyed this one!!!

waiting,,,,,waiting

I must say I was waiting for Layton....'

most book also state that a refugium is a place to house pods, snails etc, so that the fish cant eat them.

I agree with that bit, at least thats why I have one. I want a place where things can survive away from the predation in my display, specifically pods and mysiss, as food for the tank. No mention of macro algae.

The intention of my Refugium is to allow for pods to survive, sponges, things that wouldn't in the display. The effect is an unknown, however I do partitally credit it to my tanks success. What isn't an unknown is that I have more water, my water volume per fish load is higher, more water = good, less water = bad. Stability is increased, the great circle of life continues, simple.

Pie

Hey Pieman,

You know your "Homereef" link hasnt worked for about 2 years!!!

The assumption that you are making is that the skimmer pulls the same amount of waste out per unit time, independent of the concentration of waste. That is wrong.

The amount of waste the skimmer pulls out is proportional to the concentration of waste.

Think of it this way. You put 1,000 gram of waste into a 1,000 litre tank, and 1,000 gram into a 2,000 litre tank.

So the first tank has a concentration of 1 gram per litre, the second 0.5 grams per litre.

Say the first tank has a skimmer which put through 1,000 litres an hour, and say it removes 100% of the waste going through it. It's going to remove 1,000 grams of waste in an hour of running.

Now the second tank has that same skimmer on it (pumping through 1,000 litres as before, removing 100% of the waste passing through it), then it is going to pull out only 500 grams of waste in an hour of running.

So extrapolating this through the dynamics of the system, it means that the concentration of waste in the water is independent of the total water volume of the system. It is a function of skimmer parameters.

I must say I was waiting for Layton....'

same

Take the first four lines of your thread....

The end...the fish are happier in the second tank with .5 grams and you will get better growth and colour out of your corals.

As long as the skimmer gets it its all good. (Doent matter if it takes a bit longer).

But as far as the fish/corals are concerened a diluted tank is better for THEM.

I don't think you guys get the dynamics which are going on here. I've put together a spread sheet to show you. Give me a second.

Ok here it is:

http://www.nzreefs.com/images/System%20Volume.xls

Summary:

System 1 = 1,000 Litres

System 2 = 2,000 Litres

Both have identical skimmers pumping 500 litres an hour, and waste input is constant at 1000 grams per hour.

Although the one with more water initially starts off with lower waste concentration, both systems end up with the same concentration of waste in the end:

Layton

haha I thought you were joking

Nope. Engineers need to know these types of systems inside out.

Here's a better one, showing the effect of skimmer output, and waste concentration.

The system starts off at 1,000 litres, then changes to 2,000 litres after 20 hours. The flow through the skimmer and waste input is kept constant.

It's shows that the steady state waste concentration is independent of total system water volume.

Layton

the old differential equations, knew they would come in handy sometime

Yip, they show up EVERYWHERE, in the natural world. They don't just show up in voltage over a capacitor, and current through an inductor ;-)

It's pretty much a standard first order step response.

Layton - I don't disagree with you. Which isn't the same as agreeing with you. I am indifferent to the point of 'purity'.

Regarding the refugium question, to me, its a place to let my little critters get a bit bigger before my fish and corals eat them. I think this is good, I have no way to prove it, and its not that important to me either way. I am confident however that this extra volume helps me with the stability of my system, and this is of paramount importance to me. And stability may be related to Cracker saying 'dilution', but it would depend on how you interpret it, hence my indiference.

Pie

Graphs, smaphs,

Not all theories and scientific data prove certain points.

The simple fact is more water = better.

IT HAS TO.