Do I have magic water?
Yes, your water is magic...
Seriously, IMO..You are doing a good job at feeding the right amount of food to your fish, keeping your tanks clean, and keeping them stocked appropriately for the amount of space you have. Less wasted food and not overfeeding leads to less decaying food on the bottom and less fish waste. You have maintained your tanks from the get go, not allowing wastes to accumulate in them. Appropriate stocking and management of amount of food, etc., goes a long ways towards keeping nitrates low, even with skipping water changes and gravel vacs occasionally.
BTW, are all of your tanks planted?..This would be the explanation if the above is not correct..
Yes, your water is magic...
Seriously, IMO..You are doing a good job at feeding the right amount of food to your fish, keeping your tanks clean, and keeping them stocked appropriately for the amount of space you have. Less wasted food and not overfeeding leads to less decaying food on the bottom and less fish waste. You have maintained your tanks from the get go, not allowing wastes to accumulate in them. Appropriate stocking and management of amount of food, etc., goes a long ways towards keeping nitrates low, even with skipping water changes and gravel vacs occasionally.
BTW, are all of your tanks planted?..This would be the explanation if the above is not correct..