Hi can someone help me with this?

I've had two red tuxedo swordtails for the past 11 months. Both are male and are usually very active. Never had any problems with these fish up until this week.

For a few days now one of the swordtails has not been eating. It has been swimming in the bottom corner of the fish tank for a few days, and does not move much unless another fish approaches it. It does not eat at all. Once in a while the fish starts shaking like it has tremors. Also notices white stringy feces today, which is odd since in has not eaten anything in a few days. It keeps opening and closing its mouth and its gills constantly, which is odd when compared to the other swordtail.

Could this be a parasite? If so, How do I treat it?

Thanks in advance.




Tank set-up: 1 year
Tank size : 29 gallons
Fish: 1 peppered cory cat; 2 red tuxedo swordtails; three platties (type unknown)

PH: 6.8
Ammonia: 0
Nitrite: 0
Nitrate: 0
Hardness: 150
Alkalinity: 120

i had a similar problem, i changed 1/2 the water, and dint feed anything for the next day, they resumed eating afterwards, most likely cause uneaten food accumulations at the bottom of the tank
good luck