Unknown Creature Appeared

[TheFishEnthusiast]

I've had a tropical 125l tank for around 3 months. I have around 20 fish (Mollies/Platys/Bristlenose Plec/Neons) inside. Average temp is around 26 degrees. Around 2 weeks ago, I treated the tank for white spot.
 
So I got in and turned the light of the fish tank on, there was a small thin circular thing on the inside of the glass. It remained circular throughout and never stretched out. I looked closer and saw 2 antennas on top of it. I tried to catch it with my net but it fell into the gravel where it then began to go further and further down. I was unable to retrieve it. 
 
Any ideas of what it may be? I'm just hoping there isn't a disease in the tank etc.

 

[Munroco]

Could it be this?
 
Sorry couldn't resist. Don't know what to suggest

 

[nic1]

haha! well, that hasnt got any antenna! could be a snail.... have you got any live plants in the tank?

 

[eaglesaquarium]

A picture of the culprit would go a long way in terms of helping you identify your 'critter'.

 

[Ninjouzata]

As said above a picture would help a lot but I am thinking a baby ramshorn snail

 

[TheFishEnthusiast]

I have no snails in my tank (none that I've added anyway) but I do have one or two live plants.
 
My phone went dead at the time and as I was waiting for a little charge, I lost the creature.

 

[attibones]

That sounds very much like a baby snail which could have hitchhiked from the plants.

 

[SeanTrollope]

i found a worm of this decription in my tank the other day but i didnt have fish and it remained circular.

 

[Wildbetta]

Sounds very much like a baby snail. At that size on the glass they sometimes do appear as circular worms with antennae because the shell is pretty much clear at this point making it hard/near impossible to see.