not sure what start right is...assuming its some type of water conditioner (dechlorinator)?
most everyone suggests about 35% once a week for a water change on a normally stocked tropical tank...with an overstocked goldfish tank, I'd say 50% twice a week, or 100% once a week probably isn't out of the question. You could try having double filtration on it (pop another filter on? what type do you have now?)
Generally diatoms (brown algae) can be caused by not enough light and not sure, maybe too many nitrates? do you test your water for ammonia/nitrites/nitrates? Might give you an idea of just how overstocked the tank is and that no matter how many water changes and gravel vacs you do, you're just never going to catch up.
An excuse for a bigger tank??
(welcome to mft!)