hi i have a 135 gal with a breeding pair of oscars around 12 inches and a 15 inch pleco.I have been having problems with nitrates,i cant get them below 20 ppm and it rises fast.every thing elese seems to be ok nitrites 0, ammonia 0, ph 7.0. i do a 20% water change every week. i was wondering if it was possible to get and keep the nitrates at below 5 ppm. thanks

I can't see why you are worrying. We normally recommend keeping the nitrate levels below 40ppm, although even if they do rise above this, no harm is going to come to your fish short time. Remember the nitrate is not a toxin like ammonia or nitrite, it is far far less toxic. However, keeping it as low as possible is obviously recommended.

The fish that you keep will be creating a pretty large bioload so keeping your nitrate at an absolute minimum is going to be very difficult unless you carry out massive water changes every couple of days which is really not something we would recommend in an established aquarium.

Honestly, I think you should stop worrying, sounds like your water is in very good condition to me

thanks for the info i used to heve big problems with nitrates and i guess i never got over it lol. thanks

At that age, you could go to feeding every other day. That is what I do and my nitrates stay low enough that I often only have to do a water change every 2 weeks. Just a thought.

You could try doing a bigger water change, i do 50% every week

Also test your tap water, you will never get your nitrates below this level

x2 on checking the tap for nitrates.

allowing nitrates to go up, just watch for the pH. high pH will make the
nitrate deadly for fishes...