Ill Gourami

First post so bare with me
My yellow gourami has been looking rather thin of late, its fins have been down and looks sick in general. A few days ago i noticed his tail was bent at an angle and that he hasn't been swimming very much. The only time he shows any signs of been active have been when hes chased other fish away from him

Tank size: AquaOne 620 - 60 x 36 x 36cm (about 25 us gallons)
pH: 7.4
ammonia: 0.2
nitrite: 0
nitrate: 0.25
kH:
gH:
tank temp: 27C

Fish Symptoms (include full description including lesion, color, location, fish behavior):
Fish has a bent tail, looking thin, unsocialable with other tankmates, not very active

Volume and Frequency of water changes: 20% today, another one in a few days i think

Chemical Additives or Media in your tank: none

Tank inhabitants:
1x Opaline Gourami
1x Yellow Gourami
1x Indian Gourami
1x Red Honey Gourami (small)
5x Black Widow Tetras (Small)
1x Marble Plec
1x Talking catfish (i think thats what it is)
1x Bronze Cory
1x Male Swordtail (small)
2x Phantom Tetras (small)
1x Black Neon Tetra

Recent additions to your tank (living or decoration):
New plants added about 3 weeks ago and a plastic plant

Exposure to chemicals: None known of

Digital photo (include if possible):
photos taken today
any help would be appreciated, i don't know whether its old age. Ive only had the fish for about half a year. But if it's something else I'd like to try and save him

may i point out, that she is only housing some of the black widow tetras for me temporarily. Couple of days at most. Her tank is not normally that full

Slight ammonia reading water change.
Being thin, internal parasites, fish tb to flukes.
Whats it look like when the fish goes to the toilet.
Check the anus of the fish to see if its enlarged or red and inflamed.
Any other symtoms to go on.

The fish hasnt "gone to the toilet" for a while, last time it did it was quite pale and straggly. Not much to it.
Other symptoms...well its tail also has a chunk missing on the bottom and it seems to be feeling around with its "antennas"(no idea what there called) which none of the other gouramis do...no other symptoms apart from those and the others

Bless him.
Long stringy white poo can be bacerial infection, internal parasites, to constipation.
Has he lost weight to not eating.

Possibly, when he eats he tends to spit it back out as of late. If it's constipation or bacteria how do i cure it?
Thank you for the help

What does the fish gills look like pale with excess mucas, or red and inflamed.

definately red gills

O.K...its on the brink of dying now!...its just lying on the gravel...every now and then it has the odd spasm where it attempts to get back up...it's still breathing but i dunno if it's going to make it another day
whatever it is it seems to have only affected that one fish thankfully
any ideas on whether i should put some med in to the tank and what sort (prevent other fish from becoming ill aswell)

Thanks for your help ....but its too late, hes passed away now

maybe it was just old age

You will need to treat your tank for flukes.
Red gills, going thin, spitting food out is a sign of them.
R.I.P.

http/www.flubenol.co.uk/

Look under gills flukes
http/www.fish-disease.net/diseases.htm

http/www.okanagankoi.com/Flukes.htm