Starfish

Is this a good or bad starfish?

 

It is an Asterina Star.

If it's on the glass, it is probably one of the harmless algae grazing types.

 

Good starfish but sometiems can reproduce quickly. I saw one in my tank months ago and didnt see it again until the other week. I did some reading on them and it seems that a long time ago they were considered to be a very beneficial part of the CUC and recently they have been outcast and unwanted hitchhikers. One interesting theory I was reading up on as to the reason for this stated how today we have such efficient ways of sterilizing our tanks with high tech protein skimmers, pumps, fuges, sumps, chemicals, resins, etc that we did not have or use many years ago that their role has changed because of available food sources. In a sterile tank with nothing to eat they have grown a liking to corraline algaes and corals that they never did eat before as a simple means for survival, but in a tank with healthy algae growth they have a plentiful food source without having to adapt to the things we dont want them to touch.

Not sure if there was ever any studies on this, I doubt it, but it makes perfect sense to me. For what its worth I have never seen my mini star on the glass only on the liverock, but I have never seen it on a coral only algae patches.

 

They will eat zoas. I had a tank with plenty algae and still ate them, they like expensive ones......I remove them at sight.

 

I have zoas and found the starfish a few inches from the colony, never had a polyp go missing.

As with almost every starifsh, worm, snail,etc there are way too many species that look almost identical to each other and can only be told apart with a microscrope, genetic testing, and a lot of expertise. I have come to go by a very simple rule with hitchhikers in my reef. The golden rule of hitchhikers, if I see it on something I like causing damage I will remove it otherwise I just leave it be. If it is just on the glass, rockwork, sandbed, etc and I never see it on a HEALTHY coral than chances are its a harmless little critter and a good part of the CUC. If it is on a sick or dying coral it is msot likely eating the dying flesh, as any good member of a CUC would do and does not always need to be removed if you can not be certain it is what caused the flesh to die in the first place

 

Well I have found them climbing the stalks of perfectly open zoas and Pali. They climb up to the top of them and sit right on top of the polp and it slowly dissolves and turns to a brown goo. If you catch them to late. Literally they just sit on top and eat there way down them.

 

If you catch them it is not to late, you may lose a polyp or two but usually not the whole colony overnight. I am sure its possible but more than likely that would be from a zoa eating nudibrach

 

I keep a close eye on our polps and my wife does to. She actually say a zoa eating spider years ago and she dipped for me and killed it.

It seems one gets a polp nd weakens it more come after them.

 

Being that there are 100's of different types it's very hard to make an ID. When wittnessed on a coral, be it SPS or zonathids it's probably a safe bet that it is eating that coral, some are coral eaters. Blue gray types on the rocks tend to be coralline algae eaters, types seen primarily on the glass algae grazers. Population of some types can explode with enough available food.

I tend not remove them unless I see them eating a coral.

 

Every starfish eats zoas, That's why I don't have zoas.

Except Britle Stars.