Hi, this is my first post here.
I have kept one or two comets or shubunkins in a 20 gallon tank for the past 5 years. I was a beginner, have made some mistakes, and still make the occasional mistake. I'm trying to take another step toward being better at this. I enjoy reading and learning about fishkeeping and try to continually improve the conditions for my fish.
I used to use test strips for testing my water and was ignorant about water changes. In the past couple of years I have been better about water changes as I learned the whys and hows of this.
I have a simple set up: 20 gallon tank, tap water from a well, basic filter that hangs off the back. I use plastic plants, have small stone substrate, and have a wonder stone and lava rock as well as a few smaller rocks and shells. I feed flakes, small sinking granules, and brine shrimp. I keep my aquarium light on a timer as it's in a dark part of my apartment; it is on for about 9 hours a day. I sometimes experience a little brown algae; more seldom a little green algae but not nearly as much and usually only if I've been bad about cleaning the glass or decor.
Recently after having a single healthy shubunkin for about 6 months I decided to add one more to the tank. The new fish seemed to settle in fine.
Today while I was out I picked up a Master Test Kit for freshwater tanks. Some of my strips had expired and I knew they were not as accurate and so I'd put off replacing them until I had enough money for this kit. It's been awhile since I have tested some of the levels although I did have a pH kit.
My tank was good in most areas. pH is 7.6 on the normal test, although it reads 7.4 on the High Range test. Either is great for my Shubunkins. Ammonia was 0 (I did a water change 2 days ago and have never had ammonia issues) and Nitrite 0ppm.
The Nitrate concerns me. It reads 80ppm so I tested my tap water. The well water from the tap seems to look like it's in the 10-20ppm range.
I'm wondering what I ought to do to correct this, if continuing to use tap water is still ok, and how often should I change my filter media? I normally change it about every couple of months, and in between I sometimes give it a good rinse in running tap water adjusted to the same temp (while I'm doing a water change). Is this often enough? Why is my Nitrate high if my other levels are good?
Thank you very much.