I recently had 3 abino corys and two died due to a new filter. I didn't know they were that sensitive, and I had to replace my filter. Anyway I have one survivng albino cory, and he has been swimming at the top of the tank for a few days now, I can't feed him if he doesn't go to the bottom. He won't take any other foods.

I think I was waiting for amonia to go down due to the new filter. What can I do?

Yes, I know they should be in groups of 3 but I don't want to risk getting any more right now.

Why won't he search for food at the bottom?

What are your water stats in ammonia,nitrite,nitrate,and ph, do you have an airstone running for extra aeration as with the tank cycling i will be bad down below for him.

If he's at the top of the tank, I'd say the chances are good that the aeration is not sufficient.

He would also be gulping for air if aeration were insufficient. It sounds like he doesn't want to stay at the bottom where most ammonia/nitrite etc accumulates which is poisoning him (as I gather the tank's not yet cycled). You need to do several very large water changes and test your water. Get some mature media from your LFS ASAP and add it to your filter. That will speed up the cycle and may save this fish' life. If in future you need to change your filter (do you mean the filter by this or the media inside?), use the old media on the new filter or leave both filters in the tank (whether the old is running or not is insignificant) at first so the good bacteria can 'migrate' from the old to the new and you can avoid the mini-cycle. If what you eman is that you had to replace the media, in future change one bit at a time. Cut it up if necessary or keep some of the media in the tank (but outside the filter) for a couple of weeks so the good bacteria can colonise the new media as well.

no3-20
no2 0
hard 120
akl-80
ph-6.8

There is no airstone in his tank, but I have a 5 gal with a corner filter with an air pump, air stone. Should I put him in that?

I've had these corys for a year now and they seemed fine in this tank until I changed the filter.

Do you have a water test kit? Ammonia is very important to know. If you don't, i strongly recomend you buy one. It is the first thing to check when you fish are acting wierd. Your fish not eating can be a sign of either being stressed OR being sick...you really need to get this tested. Most LPS do water tests for free.

Regardless, I would say this fish is acting stressed from ammonia, especially since you just chanded the filter. I would do a partial water change.

Yes, I second that... or third it?? Anyway, do a water change immediately! You'll be amazed how much a water change do when your fish are acting not-quite-right. Then if he's still acting off, add an airstone or lower the water level a bit to make the filter splash more. If that doesn't help, I'd move him to the 5-gal until you can figure out what is wrong.
Good luck!

Also, adding the 5 gal filter to the other tank might do some good, especially if that filter is cycled and the other isn't.