How often to change water for discus fish?
That would be just over 92 gallons. That seems a little small for 6 discus, but you may get away with it if you change at least 25% of the water weekly. No matter what, weekly water changes are essential. Ammonia, nitrites, and nitrates aren’t the only things going into the water. Discus are quite touchy when it comes to water quality, so I’d err on the safe side and change 75% of the water weekly. This won’t harm the good bacteria because that lives in the gravel or sand and the filter. The good bacteria can’t live suspended in the water, it needs the solid surface to adhere to. Fluvals are a good filter, but the 405 is only rated for a 100g tank. Filter output is always less than it is rated for. I’d either get a larger filter or add a second filter. Besides, having two filters ensures that even if something goes wrong with one of them, at least you have one to fall back on.
