Reply. Hello Sandra. I'm glad to read that the gravel in your aquarium is about 1/4" thick. When you gravel wash your gravel, bits of waste
and bits of uneaten food will be removed, and this will help keep the water quality in your aquarium better for your fish.
Gravel washing will also remove huge numbers of beneficial bacteria living on the surface of the gravel, but this is irrelevant, because there are even larger numbers of
beneficial bacteria living on the BIO-Wheel in your filter. You do have a BIO-Wheel, don't you?
My container pond does not have a filter, so it does not have a bio-wheel. The waste in my container pond is digested by the beneficial bacteria living on the gravel at the
bottom of my container pond.
When I thoroughly gravel wash the gravel in my container pond, huge numbers of beneficial bacteria are surely removed.
But there are enough beneficial
bacteria left on the gravel to digest all the waste produced by the fish in my container pond.
here for more information about my container pond.
I also have several fish bowls, and they do not have a filter, but each bowl has a thin layer of gravel just like my container pond.
To clean a fish bowl I gently stir the water, which stirs the particles in the gravel up into the moving water. Then I pour off 20% of the water and replace that water with
bottled drinking water. In this way I remove some of the bits of waste in the gravel.
One time I poured 80% of the water from one fish bowl into a second identical fish bowl that was clean and empty. Then I rinsed the gravel in the first fish bowl with tap
water. I rinsed it several time and vigorously stirred the gravel until, it was very clean.
Then I poured this very clean gravel in the second bowl. In a day or two the water in the second bowl got cloudy and smelly. I think this happened because the tap water and the
vigorous stirring removed or killed most of the beneficial bacteria on the gravel.
I had done too much cleaning, so there were not enough bacteria remaining on the gravel to digest all the waste in the fish bowl. I added a couple of tablespoons of gravel from
another fish bowl, and the water cleared in a few hours.
here for more information about beneficial bacteria and biological filtration of water.
In an aquarium with a BIO-Wheel the gravel is only ornamental, but in a container pond, and especially in a fish bowl the cultured gravel is very important. So you must be sure
not to damage the beneficial bacteria that live on the gravel.
here for more about cultured gravel.