Should I do a water change?? 20 ppm consistently for 3 weeks. 75 gallon

I've been checking on my nitrates for a couple of weeks now to see how consistently I should do water changes, but every time they've been 20 ppm. I go to PetSmart to have my water tested and they use the API water test strips and they aren't the most accurate according to some people, but they still should tell me if nitrates are going whack. I first tested my water the day after a water change (25 %) and the nitrate level was at 20ppm, it didn't go down. Then a week later still 20ppm. I haven't done a water change since then and I went to get my water tested since I thought nitrates would be higher, but it still read 20 ppm?! I have plenty of fish and I feed them every day. I would have guessed that by now (3 weeks later) it would have increased to 30 ppm. I did add some pothos plants to my aquarium so could they have been keeping it low? Should I just keep on waiting, are my plants handling the nitrates? Could it be that it stays at 20 ppm because my tap water has 20 ppm nitrates?

 

Have you run the ammonia and nitrite tests? If you have 20ppm nitrates in your source water and they haven't gone any higher than that in your tank I have to wonder if the tank is cycled. If it isn't then yes, you need to be doing water changes since you have fish in this tank.

 

Have you run the ammonia and nitrite tests? If you have 20ppm nitrates in your source water and they haven't gone any higher than that in your tank I have to wonder if the tank is cycled. If it isn't then yes, you need to be doing water changes since you have fish in this tank.

Yes, it is a fully cycled tank. It's been running for more than a year. So the ammonia and nitrite levels were 0. It's just that about 2 months ago I started finally paying attention to my tank more and that's why I'm finding all these new little things.

 

Test strips aren't accurate enough to detect smaller changes in water chemistry. If I was you I would invest in a liquid test kit to test your own water. They aren't very expensive and last for a lot of tests. I would recommend either api master test kit or NT labs freshwater test kit.
Water changes do more than reduce nitrates, they also replenish electrolytes and bicarbonates that help buffer the pH. I would do a weekly water changes of at least 20% regardless of nitrate readings.
Nitrates should ideally be in the 5-10 range or lower but if you have 20 in the tap water that may be hard for you. Some fish are more nitrate tolerent than others so keeping them as low as possible is best.

 

Yes, it is a fully cycled tank. It's been running for more than a year. So the ammonia and nitrite levels were 0. It's just that about 2 months ago I started finally paying attention to my tank more and that's why I'm finding all these new little things.

Great. It is strange that you nitrates aren't going up but not overly concerning. Personally I change out 50% of the water in each of my tanks each week no matter the nitrate reading. Water changes do more than just lower nitrates. Over time things build up in our tanks that we don't normally test for and other things get used up. Water changes help to keep things balanced.

You may not need to change out that much each week. A lot of it depends on your stocking level.

 

You could also add some land plants like pothos and there is a list of many others that could help with your Nitrates. I wouldn't be overly worried about that number. Floating plants can also help suck up some Nitrates. Also from what i've heard around here some people use Nitrazorb to help with Nitrate levels especially if their coming out of your tap. I think it could be helpful if your concerned about those numbers. I would also suggest when your able to, invest in an API freshwater test kit. Usually around 20-25$ and you can test whenever u need to.