angelfish acting weird

for the past week my angelfish has been acting strange-he stopped eating and began to swim flat finally sank to the bottom of the tank and just laid there-his skin looks dully streaked in spots-I've thought e-he would be dead any day-tonight he acts like he feels better-he ate some and is swimming better--he is one of only 5 fish in a 20 gal. tank and I do regular water changes and maintenance-the numbers all look good--any ideas as to what's going on and treatment?any help would be greatly appreciated--

How big is it? Adult Angels require 10 gallons of water per fish... So if it's full grown, even if you just have some little fish with it, you might have the tank overloaded...

Also... What temperature is your tank? Angels like a warmer temperature... I keep all my angel tanks at 82-85

Keep us posted... Hopefully it'll pull out!!!

How is your angel doing now? It sounds like it had/has an issue with it's swim bladder. You might try feeding smooshed peas(no skin) or Epsom salt(not aquarium or table salt)as a bath or dip. These are usually treatments for constipation, but they may do some good for your angel if it is an internal issue.

my angelfish seems to be doing better the past few days--i have increased the tank temp. to 82 degrees as suggested--if i do the epsom salt, how would i do it? i assume just dip some water out and put the fish in with some of the epsom salt? thanks for the advice--

Here is a link to treatment for a betta. The same technique will apply to your angel.
http://en.allexperts.com/q/Fish-1472/poor-betta-drospy- Tumor.htm