Betta Not Swimming

[Pedlinger]

My female betta hasnt swam for about 4 days now.  She is just floating at the top of the tank and also hasnt eaten
Ive noticed today that her eyes are red too, completely red!  

 
So the tank specifics are:
 
120L (100wx40hx30d)
Running since Sept 2012.  23 fish.  Mix of mollies, danios, clown loach and white clouds plus 2 bettas
water tested just now, 1hr after 20% change
NO3 - 0
NO2 - 0
GH - 4
KH - 0
PH - 6.8
CL - 0
Ammonia - 0.25
Everything except the ammonia is done with a paper test kit (I know ..  liquid ones will be ordered very soon  

  )
 
Ive carried out water changes daily since the betta got sick but cant get the ammonia to 0.
 
Whats happening??  The only time she livens up is when I change the water and she swims for about 5 mins after im finished.  and then she returns to the top corner and just sits there.
 
I lost a female marbled molly in same circumstances (minus red eye) approx 2 weeks ago so something is wrong..
Could it be the amount of poo my plec is producing?  never seen such huge waste from a fish!
 
Thanks in advance  

 

[phoenixgsd]

two bettas, male or female? females can be kept in large groups to even out the agression, males should  be kept separate, your tank is only 120L  how many clown loaches do you have? they can  grow up to 10 or 12 inches, i wouldnt be surprised if you have a territory issue

 

[Pedlinger]

both females, they arent aggresive... dont bother each other or other fish at all.
I have 4 clown loach.  I know they'll have to be rehomed.  The guy in the shop told me Id easily get a couple of years out of them before having to think about size in the tank as they were slow growers.  Ive since learnt through the forums this is not necessarily the case