Nitrates - What to do about it

[howdy20012002]

I have high nitrates in all of my tanks..and haven't been able to get rid of it.
Could it be that i am feeding my fish too much?
I feed flakes in the morning and mysis in the afternoon.
All of the tanks have been up and running for a few months and haven't really had any new additions or anything that would cause problems
All my other parameters are fine...
Is there other options than water changes to bring down nitrates?
I was doing about a 25 percent water change a month
However, water changes are time consuming and a bit costly
My bio load is about average..not too high in any of my tanks
Does anyone know of any other ways to get rid of nitrates?
Any advice and suggestions would be greatly appreciated
Neal