whats wrong with my fish baby>

[mee924]

My goldfish I've had for 4 years has turned white over the last 2 months and I have no idea why. I'm in college so my dad takes care of my 40 gal tank when I'm away. I had him change the light and open the window curtains incase it was the lack of sun that caused this. It has been getting worse and now there are red patches on him. my other goldfish seems fine and so does the tetra that shares the tank. I checked the levels in the tank and they are
ph- 7.4 nitrate-5.0 nitrite- 0 ammonia-.25 and the temp is 76 degrees Fahrenheit. the filter is a cascade canister filter 700 and its cleaned every other week. They are being fed tetra pond sticks twice a day. Can anyone help?

 

[Dallascowboys16]

Hi! Based on the large size of your goldfish and the small size of the tank, the unavoidable fact of the situation is that the goldfish will produce far more waste than a tank that size is capable of dealing with. The presence of 0.25 ppm Ammonia is proof of this and is a high enough concentration to cause serious damage to the health of a fish in the long term. As far as the fish changing color is actually is pretty common with goldfish to go through such a color change at some point in their life so I wouldn't worry about that as long as he is acting normal (eating, pooping, swimming). I don't know what the current water change schedule on the tank is, but I recommend increasing the frequency of water changes to help combat the water quality issue which will end up shortening the lifespan of your fish. What is your current maintenance schedule on the tank?