Sorry to hear it still isn't doing well. If you do decide to euthanize it, I would suggest clove oil. It seems to be the most humane method.
First you need to pick up a bottle of clove oil. You don't need much of the stuff, but it has to be added gradually to keep the stress on the fish to a minimum.
Next, you will want to place your fish into a smaller container full of water (I have a one gallon tank used specifically for the unfortunate event of euthanizing fish).
Next you need to mix 3 drops of clove oil with a small amount of water in a separate container. Make sure it is mixed thoroughly, because it is an oil and it would otherwise simply float on top of the water.
Add it slowly into the water with the fish you intend to euthanize. Stir the water slowly with your fingers or a chopstick or other rod-shaped object. After a minute or so you should notice the fish getting lethargic. At this point, slowly add another mixture of water with 3 drops of clove oil. Slowly stir like before.
It will get more and more lethargic and will eventually fall asleep and go belly up. Add 3 more drops. It is sad, but at this point the fish feels nothing, and if you wish to step away for a few minutes to give the fish time to die, do so. When you check the fish, check for gill movement. If there is still gill movement, add 3 more drops.
When the fish is no longer moving its gills, it is gone. Be sure to wash or dispose of any instruments or containers that came into contact with the clove oil mixture.
It is sad, but again, after the initial dose, the fish will feel nothing and will peacefully drift off to sleep.
On a lighter note, if your current Bolivian survives and you plan on getting more, I feel like you could comfortably keep 3 adult rams in your 120L. Bolivian rams are really hard to sex when they are juveniles. If the rams at your lfs are juveniles I would recommend indiscriminately buying 5 or 6 of them. When sex becomes apparent, trade back the 2 or 3 that you don't want. It's even possible that all 5 or 6 could get along just fine in a the tank, depending on your decorations.
I know. Can't be nice starving to death. I only did it when it was really called for.
There always a debate on it. But I used the ice method. Some use clove,oil. Or chop there heads off.
But I couldn't fetch myself to chop the head off.
is he a bit more active yet.
Do you know how long the medication takes to kick in?
He has seemed slightly more active but it goes through phases of staying still and moving about. It seems to rely on the current to move rather than move itself around which isn't a good sign.
In humans I know antibiotics can take up to 2 weeks to begin to take effect. However, as the fish is in 27 degrees C water and is considerably smaller than a human, it may synthesise quicker due to its faster metabolism. This is just a logical guess. Hopefully I'm right!