with the large tanks u describe i really doubt they need weekly changes presuming they are planted
It is true that live plants do impact on this due to their natural water filtration capacity, but at the level most of us stock our tanks with fish, this is not a safe practice.
so lets say you have 4 50+gal tanks i would do one a week perfectly acceptable and less stressful for your fish |
personally i never change water unless the nitrates get too high for my liking
other than removing approx 15 litre to clean my filters i dont ever change water without a v good reason
As jaysee correctly mentioned, there are important reasons for weekly water changes. Using higher nitrates as a reason is not advisable, since by the time the nitrates have risen the damage to the fish has been done. And contrary to what one may read elsewhere, nitrates do harm fish long-term.
Stress of not doing water changes is much more significant that any stress from a water change. As most of us have learned over the years, fish become used to them, and some will even "welcome" the process. If you are in the tank but not chasing after the fish, they learn that it is not a danger.
The stuff you cannot measure that accumulates in an aquarium from fish has to be removed, there is no other way to handle it. Those of us who have worked in sealed offices with "air conditioning" but no opening windows know what this is like compared to fresh air from an open window. In the closed aquarium this is magnified many times. Stale water is detrimental to all fish, and the daily accumulation of stuff worsens it daily.
also although plants enjoy neutriants from a water change they also feed and need nitrates |
weekly changes on large tanks will leave nitrate levels extreamly low for your plants to thrive
While some plants will take up nitrates, most prefer nitrogen as ammonium which they grab from ammonia and plants can out-compete Nitrosomonas bacteria for the ammonia. Studies have shown that once the ammonia is insufficient, many plants turn to nitrite and then nitrate. Those with high-tech planted tanks dose nitrates since this is safer than dosing ammonia or nitrite, and the additional nitrogen is essential to balance. But there may be a toll on the fish.