I have a fancy tailed goldfish. He's about 2.5" now. I have him in a 5 gallon tank. Temp is 68 degrees, ammo. 0ppm nitrite 0ppm. I do a 10% water change a week. He acts dead sometimes. I come in the room and he'll be vertical in the plants. He really looks dead but I walk over and tap the glass and he starts to swim around and acts fine. I've tested the water over and over again and nothing is wrong there. He's been doing this for about 3 months, so I don't think he's dying. Is he sleeping? By the way the tank has 3 stage filtration. It's a Regal Galaxy 5. What should I do if anything?