Not aptasia?

[vetteguy53081]

Here are my two new guest.

Aptasia

 

[vetteguy53081]

Aiptasia.
Also, Aiptasia:

We may have to agree to disagree.

I've been in the hobby for some time as well, though didn't encounter these near as often at the start.

Ill say what the problem and difficulty is: Coloration of Aiptasia is due to the presence of Zooxanthellae (microscopic photosynthetic dinoflagellate alga - species Symbiodinium microadriaticum). For this reason Aiptasia that live in well lit areas of the aquarium are usually light greenish brown to dark brown. Aiptasia in areas which receive less light are typically medium to light brown or tan in color. Aiptasia that live in low light areas or areas without light can be transparent appearance or white. Often an anemone's column or stalk is lightly marked with parallel longitudinal lines. Sometimes white or light green flecks may also be present near the tentacles, and it is not unusual for juvenile specimens of aiptasia to be entirely covered with them.
can cause a lot of debate

 

[John A!10]

Just kill it don’t take any risk. When I first started the hobby I thought I was some expetion. I did everything super cheap and carelessly thinking it would work out. I saw one aptaisia left it for a while it turned into two, four, to hundreds of aptaisia. After setting the tank backup I haven’t had any issues yet but I’m killing any aptaisia at first sight.

 

[LegendaryCG]

I also have cup coral in my tanks because I have actual live rock from the Gulf of Mexico. It looks *A LOT* like aptasia, but tends to be a little different colored (mine are a translucent blue) and has a skeleton. Very easy to mistake it, pretty cool uncommon coral though.