- Joined
- Oct 6, 2007
- Messages
- 260
- Reaction score
- 162
Low oxygen, high nitrogen can also cause too much bad PE.
Veron talked about this in one of his books. The corals do not NEED to eat and seldom do in the shallow, clean reefs of the south pacific (he is talking about acropora). I think that he called it respiration, but that is not technically correct (I guess) and gas exchange is more like it. He also talked about how corals that could double their mass in several months would rarely risk extending their polyps if they did not have to - yes, it is a risk.
All of that said, it is usually a good sign... but be smart, understand what is happening and keep your eyes peeled for the other signs of unhappiness. Generally speaking, if a hairy acro has no PE all of a sudden, then you need to notice... same thing with one that never had much PE that all of a sudden has a lot.
My apologies if I mentioned this already, but I compare PE to full mantle extension in clams. This can oft be a sign of too little light, but people generally think that this is a good think since they are "out all of the way." Healthy clams do not often need to be fully extended to get enough energy from zoox under good lighting. Either PE or full mantle extension can be a good or bad sign.
+1.
Very well said.
It costs coral energy to extend its polyps. The rule of thumb for marine animal is that they dont spend energy if they don’t have to.