What constitues 'overstocked' and what does it actually mean?

They fight each other till one of them dies.

 

The thing is, overstocking isn't just one thing. It's everything mentioned above. If any happen, you're overstocked.

Lack of oxygen, lack of filtration, lack of physical space, lack of territorial boundaries....it's really "If any of the above, you're overstocked", rather than "overstocked" as a concept being a monolithic, static thing that can always be measured with a "yes" or "no" answer, and that answer will continue to apply for the tank years down the road.

 

do some corals filter water and/or consume certain bad water characteristics? ie - how chaeto consumes bad water chemicals?

 

Well, chaeto will add oxygen to the water, while removing nitrates and phosphates. Phosphates aren't too much of an issue for fish, but nitrates definitely are at high enough concentrations. Corals won't do this, as they don't photosynthesize enough to beat out algae that would grow in the tank.

 

very good explanation. thanks. this makes a lot of sense to me now.

 

Xenia absorb nitrates I think.

 

All photosynthetic corals will absorb some nitrates, but not enough to have a significant impact on water chemistry.

 

what is their output? oxygen?

 

No, they don't "output" anythings, except possibly waste. The nitrates are used for energy/food whatever you want to call it. Don't confuse photosynthetic with photosynthesis. Plants undergo photosynthesis ultimately producing Oxygen, corals are photosynthetic, meaning they obtain energy from the sun.

 

They're only different because one refers to the process, while the other refers to something performing the process.

The difference between corals, plants and algae is absolutely none when it comes to which can be described by the term photosynthetic, and all of the above perform photosynthesis.

The difference between corals and (plants and algae) is that corals have xooxanthellae which perform photosynthesis, then the products, oxygen and carbohydrates, are used by the actual coral tissues as well as the xooxanthellae. In (plants and algae), there's so much extra being produced that they use the huge surplus to grow and astronomical rates, wherein they usually get eaten by something else.

In other words, the of production to usage is much closer in corals than it is in (plants and algae). Corals usually have a produce:use ratio of anywhere from 1:1 to 0.1:1, whereas plants have a greater ratio, more like 1:0.5 or greater. Plants produce extra; corals don't.

In other words, plants and algae produce lots of "extra", while corals do not, because the ratio of chloroplasts to the amount of tissue supported by the chloroplasts is a few orders of magnitude different.

I tried explaining this a few ways just to make sure it was clear; let me know if it isn't.