If you have nitrites in your tank, it means that it is not fully cycled. You should perform regular weekly maintenance on your tank which includes changing at least 50% of the water each time along with removing waste and debris.
When adding the new water back to the tank, ensure that you add the recommended dosage of water conditioner such as Prime or Amquel+
PH,ammonia,DH,nitrites and nitrates. look for "tetra easy strips" is pet stores
In a marine REEF aquarium nitrates should be kept as close to 0 ppm as possible. In a fish only marine aquarium you should strive to keep your nitrates below 20 ppm.
Water changes are the quickest and easiest way to lower nitrates in a marine aquarium.
Water changes are the best way to lower nitrates in an aquarium. Especially when the water is changed using a gravel washer, or aquarium 'vacuum'. Fish wastes can only really be broken down into nitrates (except in special marine aquariums). So the easier way is through regular water changes.
nitrates among other things
Do not add chemicals. Grow some aquatic plants.
If you have never set up a freshwater aquarium before, it would be best to call an expert. Check Yelp listings for some freshwater aquarium stores in your area. You will find reviews on them and choose which company is best for you.
food chain and food wep
To maintain an aquarium with no nitrates and ensure the health of your aquatic pets, you can do regular water changes, use live plants to absorb nitrates, avoid overfeeding, and properly maintain your filtration system. Monitoring water parameters regularly and keeping a balanced ecosystem will help keep nitrates low and your fish healthy.
Nitrates can enter a freshwater source through runoff from agricultural fields where fertilizers are used, as well as from leaking septic tanks, livestock waste, or wastewater treatment plants. Once in the water, nitrates can lead to eutrophication, which can harm aquatic life and degrade water quality.
Snake-heads which are now illegal and that's if your talking about freshwater aquarium.
Shrimp and goldfish are not compatible in a freshwater aquarium. Goldfish are known to eat shrimp, so it is not recommended to keep them together in the same tank.