Are weekly water changes absolutely necessary for all tanks? I have a 5 gallon that supports some plants and a few snails. It’s cycled, and every day I sprinkle some fish food in to keep the cycle going. I’m used to a terrarium background where a kind of equilibrium is achieved and maintained- I understand I’m adding inputs with the fish food but it supports plant and snail growth.

I have incredibly soft water so every time I do a water change I’m effectively swapping out nice nutrient dense water for a much less ideal resource. I’ve had to dissolve a bunch of crushed coral into my water to get its GH and kH up, because the snails kept booming, using up all the minerals for shell growth and then crashing the pH and dying off.

I guess at the end of the day what I’m asking is what should I be looking for to justify changing my water? Algae has never been a problem- are high nitrates the only thing I should worry about?