My nitrate keeps rising on
my 50-gallon (190-liter)
tank, but why? The nitrate
rises, then I do a water change to lower it,
but then it slowly rises over the space of
a week again. How do I get it to zero and
keep it there?
Though there is not enough
space to publish them here, I
reviewed the test results you
included on your tank showing
a nitrate reading of 30 ppm before a water
change, and then the same reading of 30 ppm
some time later.
A 20-percent water change should, logically,
reduce the nitrate level by 20 percent. So
ideally, if it was 30 ppm before, it should be
about 24 ppm now. However, this assumes that
your replacement water has zero nitrate in it.
Most municipal tap water has high levels of
nitrate. If you’re removing water at 30 ppm
nitrate, and putting 30 ppm back in, you’ll
never lower it. If you want to lower nitrates
in your tap water, you may need to look at
filtration options for your replacement water
supply, such as employing an RO filter.
You also indicated some worry about some
pH swings that showed up on another tank,
Tropical Fish Hobbyist www.tfhmagazine.com 7
Corydoras catfish are known to spawn in the aquarium after water changes, especially when cooler-than-normal replacement water is used.
The popular sunset platy is likely a hybrid of two or more Xiphophorus species.