My friends Goldfish is in an approximitly 10 gall on tank filtered and every thing. The fish is a 7 year old fancy. She cleans it every month and does water changes weekly. She feedes it normal goldfish food and nothing else. Recently her fish has slowed down. Lokks normal. Im going to test the water and get a picture as soon as I can. Is this old age? Is there any thing That she can put in there? Would a snail be ok?