Its actually 13.5liters which is 3.5 gallons

the camera makes it look small
Im okay doing 100% daily changes, i just scoop him into one of those little plastic take away containers and do what i have to do, float him in the new water to get the temp and slowly add the new water to his cup over 30-45 mins =) works wonders its just a time constraint i have with work, some days im working until 12am and i cant go about fussing with the tank and wake up the neighbours (apartment living FML)
He certainly has perked up since being home with me instead of stuck in a tiny over crowded tank