New leak

Since a few weeks ago, I have finally noticed that the fish has grown physically, maybe a few centimeters long but with mild changes on his color texture. What was missing on my last post was the amount of changes of water i make due to the build up of algae/bacteria and other micro organisms. i usually change my water once a week and do it on the weekends. But since it has been relatively cold these days, my procedure has changed to one and a half weeks. This is because there has been no growth of algae/bacteria because of the less frequent UV rays that favor algae growth so conditions have not been favorable of recent which in turn is favoring Nemo and I.
Yesterday i found the fish behaving in a abnormal manner, it was right at the bottom of the tank doing something weird, I could not tell whether it was feeding on the remains of it's food(which is unlikely because he is passive eater and finishes his food the moment i throw it into the jar) or something else. I'll have to keep monitoring his behavior with regards to this piece of the puzzle. When i change the water to clean the tank, i remove 100% of the water to ensure credibility and reliability of fresh clean water for the fish and to kill any possible harmful filth that i may not be able to pick up on which may be sickening to the fish.