Regarding new tank

What are your parameters? If your tank is cycling, that clown should not be in that tank.

However, the behavior you are seeing is somewhat typical of clowns when introduced into new tanks. It is essentially being hosted by the corner (comfort zone). The almost jumping is concerning and could very well be an indicator the fish wants out of the unsatisfactory water. If you want to do the right thing for the fish and your tank, take the clown to your LFS for future credit or have them hold it for a month or so until your tank is ready.

I think its still too soon to say the skimmer isn't working but as previously mentioned, these are now known to be much use in the hobby. Theoretically, you should see some green/brown skimmate by now. There are mods you can do to that skimmer but I am not exactly sure what they are. I'm sure you can find them with a quick google search.

The strings look like dead/dying algae or sponge. If the later, a dying sponge can cause a fairly significant spike in ammonia.

The rock is a rock. It can't die.

The rock does look rather dirty. If you create a lot of water movement around it does it cloud the water? Something just looks off in that picture.
Otherwise it is a toss up without better pictures. Could be what Greech said. Could some form of worm(s).

Sorry I can't see the updated pics.

You're doing the right thing by getting the clown out for now. If for ant reason, you could potentially be starting your tank off on the wrong foot by having to feed and the waste from the fish. There is no reason to freek out. There may just not be enough buildup yet for your skimmer to work as expected. Your rock is fine and will continue to cure/mature (all it needs is water flow and a somewhat stable temperature). St this point you should be focusing on testing your water for ammonia, nitrite and nitrate every other day to determine if the rock you bought was truly cured or if your tank is in a full-on cycle.

Most likely.

That water looks really cloudy in the pics.


Sent from my iPhone using MonsterAquariaNetwork app