What are the tiny little organisms in my tank?

[mgudyka]

I have a 10 gallon tank that I have been preparing for a little while now to eventually put pea puffers in. Right now it is basically a bladder snail breeding tank because I have hundreds of tiny baby snails in there. In staring so closely at all of my little snails, I have noticed there are other things hanging out in the tank. There are some tiny worm things, at best only a few mm long, that are on the walls of my tank. I think I have also spotted what I learned online is a hydra. I have only seen one of those but I am sure there are more. 

 

1. What are these things?

2. Are they dangerous to my future fish? 

I assume they hitched a ride in on the plants I put in there because the only other objects in the tank is driftwood and rocks and those were boiled before setting foot in my tank.

[Schwack]

Hydra won't bother anything except baby fish/shrimp. They're a snack for some fish too. If I had to guess, you're looking at detritus worms crawling about on the glass. They're a normal part of every tank I've seen and also provide occasional fish food. However, if you see worms that have clearly arrow-shaped heads, you might be dealing with planaria. There are plenty of pictures online to compare against your worms. They stand out from detritus worms very clearly.

[SWilson]

The worms could be detritus worms, if they are skinny and tubular.  Could be planeria if they are on the sides of the glass and if they are more flat and have an arrowhead on one end.  

Neither I think would be harmful to pea puffers.  But you can get rid of them by gravel vac'ing.  The pea puffers may even eat them.  

Planeria are more known for being harmful to shrimp, and will predate on shrimp when they are vulnerable after a molt.  They are carnivorous and will prey or sick or weak animals. 

[FriendlyLoach]

SWilson is correct. The first pic is planaria while the second is the detritus worms. 

[mgudyka]

Thank you @FriendlyLoach, @SWilson, and @Schwack. I'm glad I don't have to worry too much. I don't plan on having shrimp any time soon. While I can't control reproduction on a fish, if I am concerned about surprise fry, sounds like a water change and a breeder box will go a long way.

[mgudyka]

Still can't figure it out 

[Emika_B]

mgudyka - I had similar tiny white filament-looking critters on my glass, too.  I'm guessing they're a kind of detritus worm because they disappeared  after I stopped feeding the tank.  There were no fish at the time, just a zillion snails.  I wanted to slow the snail breeding down so I stopped feeding them.  Either the worm things went away because of this or the snails ate them because they were hungry.