How long have you had it?
I got two about 3 years ago. The larger on expelled shortly after being placed in the tank. I did a 50% water change when mine expelled. I was told that it would not poison the tnak and it didn't. I have not had a problem with either of them since then.
I haven't seen the larger one recently but still see the smaller one. They are often in the back of the tank behind the rocks for weeks before they come back out front again.
It all depends on the type of cuke you have as to whether it will poison the tank or not. By now you know. I hope you have not any problems.