Different parameters are tested at different times.
pH, KH and GH get checked about every 4-6 weeks. Nitrates get checked about every 2-3 weeks. Ammonia and nitrite are only checked on cycling tanks or if I have seriously disrupted the biofilter.
The only time I test water is when a tank is cycling or when there is a problem with the health of one of my fish.. I've been doing this a long time and feel that it is not needed unless there is a problem. However, a newbie should be checking their parameters regularly until they get the hang of the hobby..
I test my rays tank before every weekly large wc. Mostly for nitrate. But every once in a while I will run a ammonia test. I testm y tap water almost as often
newbie here...I test weekly and everything has been stable. I change 10-15 gallons a week and vacume around the rocks at the same time and once a month i do a 20 gallon change with all the rocks pulled. Hopefully that is enough...the water never seems to be all that dirty.