My guess (and I am by no means an expert here) is that there is some kind of deep infection (fin rot) going on here with this poor fella. I am surprised he has never had fins (from what I read) so that makes me inclined to believe he will never recover? But you want to try, right? I mean, look at Stine's poor little Albert! Look at how far he has come! That ought to inspire you!
Do you have a hospital tank? Can you isolate him? A 10 gallon tank with a hood and a heater shouldn't really cost you more than $25 and maybe a small cave for him to hide in will help. No gravel, no other décor. A sponge filter in the corner will aid in the filtration (no carbon as it will filter out any meds).
Do you have a reliable Local Fish Store (LFS) other than Petsmart? Thankfully we have a great one here where I live and I'm really lucky, as they have saved many of my fishes with their sage advice! LFS also have better medications.
The water quality is also an issue, less than pristine water conditions will not allow the situation to improve. 68 degrees is much too cold for any tropical fish. The water needs to be in the mid 70s, so at the very least a new heater is necessary.
I have had very good success with Kanaplex (kanamycin). Raise the temp to about 80 degrees, and do six straight days of treatments (not every other day like the package says). Again, it is more economical (and safer) to put him in his own 10 gallon tank than it is to treat the entire big tank. Makes daily water changes (necessary with the treatment) much easier too. I would think it would take more than just six treatments though, this infection has taken a deep hold on him. Drs. Foster and Smith may carry this medication (
http://www.drsfostersmith.com/ ).
Or...you could leave him alone, keep his new home very clean, regular water changes, monitoring, make sure the filters are rinsed out weekly and changed out monthly (but not all at once!), and keep a good diet going.
I feed my synos zucchini (which they LOVE), peas, and sweet potato. They will take big bites out of the zucchini, and I have observed my Featherfin chewing on the sweet potato. Peas disappear too. I have also put algae sheets in the tank which they eat heartily (but they make a mess so I don't do it very often). I have also had much success with Omega One frozen foods (bloodworms, and the Freshwater Community Formula; I also use the Marine Veggie Formula). Those are available at Petsmart. Most synos are omnivores who need both vegetable and meat in their diet. Pellets and algae wafers are good, but it would definitely not hurt to supplement his diet with fresh veggies (oh and the love melon too, cantaloupe seems to be a favorite) and frozen foods too.
Good luck! Let us know how things go!
.
