If he's laying on his side, it sounds like a swim bladder issue. You can treat that with epsom salt and warm, clean water. The following information was given to me to treat my fish for sbd from a moderator on this board called oldfishlady:

"I would use a small container that can be floated in a heated tank to maintain temp of 76-77F and cover it with plastic veggie wrap to retain heat/humidity for the labyrinth organ. He needs to stay in the covered QT floating in the heated tank-in the Epsom salt/tannin water for the duration of the treatment period.

Premix the treatment water in a 1gal jug of dechlorinated water-Add Epsom salt 3tsp/gal and a tannin source-either IAL or dried Oak leaf. Let this steep for 30min and use this for 25% water changes every 15min for 1 hour today. This will get him properly acclimated and start the 10-14 day treatment.
Tomorrow-using the premixed treatment water make 50% daily water changes."

There are other ways you can do it, but this is a good start.

 

Do you just use regular epsom salt or something special for fish? For a 5 gallon tank, how much would I use? Or I guess the question would be for the small container, how much epsom salt would I need to use? How long is the treatment period? Do you feed them at all during that time? For the veggie wrap, do you need to poke air holes in it? I'm totally new at this so I want to make sure I do it right! Thank you for your response!

 

You can use regular espsom salt just make sure it's unscented. You can premix 3tsp in a gallon jug and just pour what you need into a small container. If you are going to treat the whole tank, start with about 1 tsp per gallon today, and slowly up the amount everyday, until you reach 3tsp per gallon. You can leave epsom salts in the whole tank indefinitely, but it might be better to start with treating him in a small container first.

 

For the small container, are you talking a cup like they come in when you get them at the store? How many days should I do the epsom salt? Until he seems better or a specified time? For the plastic wrap on the top of the small container, do I need to put air holes? Again, thanks for the help!

 

The Epsom salt should be 100% pure magnesium sulfate. (No dyes, perfumes or additives.) You can get it at a grocery or drug store. (CVS, Walmart, etc.)

You can use Epsom salt as long as needed. Has he pooped recently? I would keep him in the Epsom salt until he pooped AND he wasn't swimming sideways.

As suggested, mix up some Epsom salt in a container of water. I, personally, would start by adding 1 teaspoon Epsom salt into 1 gallon of water. Mix well. The salt needs to be completely dissolved. Make sure the water is at the same temp as his tank water.

Can you use the old 1.5 gallon tank as a hospital tank? That would be the ideal way to treat him. You could simply put the Epsom salt water into the small tank, then acclimate him the same way you'd do a water change. (Floating his cup, then adding small amounts of water from the tank into the cup, over the course of at least 1 hour.)

If for some reason you can't use the 1.5 gal, you can float him in a plastic cup, using the tank water. You can use the cup he came in. Fill the cup about 2/3 full, then put the lid loosely on the top. (The lid should have holes in it.).

Some fish get stressed out by clear cups though. If this is the case, you can use a regular opaque plastic drinking cup. Fill it about 2/3 full, then put the plastic wrap on top. Yes, you can put some small holes into it. The purpose of the plastic wrap is to (a) add humidity to the air, and (b) keep him from jumping out.

Slowly acclimate him to the Epsom salt, just as you would during a regular water change. The process should take about an hour, as you remove water from the cup, and add small amounts of Epsom salt solution.

Do frequent water changes, using the premixed Epsom salt solution (1 tsp per gallon). If this doesn't work, you can increase the concentration of the salt. The maximum amount I've seen recommended is up to 3 tsp per gallon.