I assume that this question arose when an aquarist discovered [tag-self]Aiptasia[/tag-self] in his/her aquarium and was hesitant in destroying them, or an article or comment had been read. I have no hesitation in attacking them, as left to their own devices they can spread alarmingly, like rampant aquatic weeds.
First of all, what are Aiptasia? They are small anemones that are clear in appearance (there are variations), and that have quite long tendrils. Another name for them is [tag-self]glass anemone[/tag-self], which is a good descriptive common name. They are also known as [tag-self]rock anemones[/tag-self].
Returning to the question of filtration, it is true that one or two advanced aquarists have mused over the possibility that Aiptasia anemones could be useful. Left to multiply, and kept in a separate small aquarium in the systems circulation, the seawater would pass through a sieve of ‘collecting tendrils’. This would provide even more anemones to assist in the filtration work and, theoretically, better seawater.
I don’t actually know if any experiments down this line have been carried out by the same advanced aquarist(s). Perhaps not, perhaps it has remained just a possibility. I’m not going to challenge the theory of potential assistance from the anemones, and at the same time I am not going to try it.
As far as I am concerned, the little blighters can keep out of my aquarium and, when I see one, it is in for a rough time and a quick exit! I think I can safely say that, for the majority of marine aquarists, and for whatever type of system they have, reef aquarium or fish only aquarium, the best action is ‘get rid’. This can be done naturally or with the aid of science. As already mentioned, left alone the anemones can spread rapidly.
Perhaps in the future the anemones will find a place in the filtration system. Marine systems are becoming more ‘natural’ as time progresses. For the moment, for the great majority of us, they are a no-no.