Cow fish will grow too large for a 25 gallon aquarium and can really mess up a tank.
In saltwater, 25 gallons is not large at all but you will be able to get away with a pair of ocellaris clownfish and a goby species.
You cant really keep more than 2 clownfish of any species in one tank. That is alittle small being less than 20 gallons. It can be done but the harder question is can you handle a such a small saltwater aquarium as in saltwater this is kinda an advanced aquarium as water is affected greater in...
Saltwater aquariums are more expensive and more difficult than freshwater aquariums and if your fish are dying then this is not a good first step. Also it takes months of research and more than a simple, i want a clownfish.
Saltwater tanks need bigger tanks, The smaller the aquarium the harder...
Basically it is a normal response. When fish rest, even more so on newer fish, they will go to where they feel safe and for clowns they will typically go to the corner of the aquarium as it has two sides of glass which they can feel safer.
They will eventually grow out of this stage but...
possible yes but practical no...
Anemones as im sure you know, need high lighting upgrades which is not fisable for a 2 gallon. Plus most anemones will need much much more room than 2 gallons.
Clownfish will be stunted in a 2 gallon but yes they can stay in there for a few days so i guess it...
might be red slime algae which is bad, you can buy removers.
Cleaning fish refer to parasite remover fish, but cleaner wrasses do not do well in home aquaria.
Clean up crews are what you are looking for. Snails, hermit crabs, etc..