Hi everyone! i've had a young, small golden fantail for about 6 months now. he's been living in a 10 gallon aquarium. about 4 weeks ago he had been living in a small 1.5 filtered aquarium while i was moving, and has since then been relocated into his larger home. he was doing fine in the large tank, and the tank cycled.
a week ago he started getting really listless, and settles on the gravel and won't move unless he's roused. then he's active and grazes a round a little before settling again. i've looked at him closely for signs of parasites or bacterial infections, but his skin looks healthy. the only thing that seems a little wrong physically is that his one eye seems to be popping out a little, but not insanely. i don't have a water test kit but i'll get one today. for two days i've been doing water changes, and this morning i vacuumed the gravel. i've got an oxygen stone running as well. i've cut back on feeding (so i've been assuming this is a water quality problem). any advice? i want to save my little guy ):
i know dropsy can start with eye popping, but so far no pinecone body. i'm going to get some aquarium salt today as well to try and help with any stress and draw out swelling behind the eye. should i get antibiotics/antiparasitics as well? or wait until i'm sure its parasites/bacteria?
also, i'm concerned about going overboard on the water changes. i did about 20% this morning, then vacuumed. so it may have been more of a 40-50% water change. the water i'm using has been out for 24 hours.

Let's get your water tested asap before doing anything drastic. Definitely don't add any medication or other major change (e.g., raising temp) until we know what's going on. My guess is that you have an ammonia/nitrite spike since you moved him recently to a 10 gallon.