Join Date: Nov 2014
Location: Port Townsend, WA
Some people say they don't change their water but we all wonder what there tanks are really like.
When water evaporates the amount of total dissolved solids (TDS) becomes a higher percentage. If there is something a little bad in the water in your area (mine has a higher percentage of arsenic) then that gets concentrated. If you just add more water it only concentrates in a higher percentage. So that is one reason that we change between 20 to 50 percent per week.
Plants use up nutrients in the water. When they are gone, the plants look sad. They drop their lower leaves, turn yellow or get spots and slowly die. The new water you put in when you change the water has some nutrients for the plants (also depending on where you live) but not all. And so we add nutrients to the water.
Nutrients that are not in our tap water are potassium and some others. Hopefully someone smart will chime in on this, but I bet you can find it if you research the fertilizer forum.
I have low tech tanks with high lights, this also causes a problem with not enough carbon (CO2, carbon dioxide) in the tank. Many people add Seachem Excell to their tanks to offset this.
I'm no expert but I'm sure I will be corrected on here. My personal advise is to change 30% of your water once a week and use ferts in half dose of what they recommend on the package. A 125 gallon tank is a great stable and solid amount of water. You might have to keep a notebook and not change too many perimeters at once to nail your needs. Got any pictures?