Does Chaeto need water changes?

Strange question I know since Chaeto is suppose to clean the water hence reduce the need for frequent water changes. I have a real hard time growing chaeto, but seem to have noticed a trend. My tank is very clean, I don't grow much algae in the tank or sump and all my inhabitants do well. The fact that the tank is clean, I can sometimes go 2 months without a water change and still show very low levels of phosphates and nitrates, I do dose alk and pretty much do water changes to replenish trace elements. The only thing I can't grow oddly enough is chaeto. It seems to go through phases where is grows alot and then shrinks to near nothing, then grows back and then shrinks. I just did a water change recently and the chaeto seems to be growing back so I was wondering if the water change is replenishing something the chaeto needs that I could just dose instead. I currently dose Kent Iron and Manganese so it's not that.

Any ideas?

 

How stocked is your tank? If the inhabitants aren't producing enough waste thus producing phosphates and nitrates it might be starving little and depending on what water you use Tap/RO/RODI it might be getting a little extra from the water especially if your using tap.

 

I've heard of chaeto going through "growth phases". To be honest, if your water is clean, I wouldn't worry about the chaeto growth.

As far as what may make it grow faster after a water change_ are you using RODI water? Do you stir up any of the sand when you do a change?

 

Stirring up no sand, using RO\DI and it's a 29 Gal tank with a 20 gal sump. I have 1 fangtooth blenny, 1 pajama cardinal, 1 ebli angelfish and 2 blue saphire damsels. Also a bunch of corals including some xenia which may be stealing the nutrients/

 

I run an overside skimmer. And have 0 nit 0 phos. And my chaeto does not like to grow. I also have 140 gal of water with only 2 clowns 1 anthias 2 mandarins. So SUPER LOW bioload. More fish would probably help it grow better.