Plecos are a no-no......
Exceptions are the bristlenose/pit bull plecos. Anytime I suggest plecos in the same breath as golds..these are the ones.
Otos and hilstreams are water quality sensetive, plus otos are snack sized.
Goldfish are carp..indescriminate bottom feeders. what will fit in the mouth becomes lunch.
Yawp! Go snails and shrimp so if the golds eat them, your feelings are spared and they cannot harm your golds.
Wih 25 gallons you have very little options. You already are at two fancies period and a possible dwarf bristlenose pleco. Goldfish rule of thumb is 10 gal
/FISH. Most prefer 15gal. Golds are so messy that many bottom fish become ill with them, and smaller fish are often snacks time to time.
The best thing to keep with fancy goldfish are fancy goldfish. Because they are
1) messy (heavy filtration and space needed for them alone)
2) high oxygen users (hence the space requirements..they need lotsa surface space)
3) highly bred to a slow form that makes them lose out to faster fish at dinner. Even faster forms of golds like koi and comets are bad. Don't mix fancies with any fish but fancies..not even other golds. koi and comets are known to chew up a fancy and devour fancys alive.
4) need cooler temps than most fish
5) they like harder water than most other commonly kept fish and respond best to treatments that other fish succumb to (copper and heavy salt)
6) are carp and will
snack on smaller gold-safe tankmates
You also have to be selective with plants since goldies are omnivourous..they even eat certain types of algae themselves.
Personally, I 'd say get good filtration and have just three golds and some shrimp and maybe snails and make up the sparseness by decorating it beautifully.