How do Trachy's and elegance grow??

Possibly a stupid question but I have a specimen of both and was wondering how they grow out.They both appear to have a cone shaped skeleton which I have buried in my substrate.Does this skeleton increase in size or does the fleshy portion continue to expand out of it? or Both?

I appreciate any helpful replies.

 

both, but it's amazing how much flesh they can get if you feed them right.

 

I thought this paragraph by Wikipedia did a good job of explaining it.

Formation of the calcareous exoskeleton involves deposition of the mineral aragonite by the polyps from calcium and carbonate ions they acquire from seawater. The rate of deposition, while varying greatly across species and environmental conditions, can be as much as 10 g / m² of polyp / day (0.3 ounce / sq yd / day). This is light dependent, with night-time production 90% lower than that during the middle of the day.[8]





Ideal levels of calcium, magnesium and alk really affect the growth rate. Replinishing the trace elements is very important as well.

 

Thank you both!!