Nitrate solution for freshwater tank

Question
Hi, My name is bryan and i have a 55 gallon freshwater tank. I have 2 kenyi cichlid, 2 acei cichlid, an electric yellow cichlid, an auratus cichlid, 2 zebra cichlid, a bumble bee cichlid and 2 chinese algae eaters. I use a marineland penguine 350 filter which after about six months of use took the biowheels out and a undergravel filter with a marineland 170 powerhead.  My ammonia and nitrite levels are fine due to the excess of bio filtration i have but my nitrate levels are at about 180 ppm and no plants will survive cause the cichlid eat them.  It is not a drilled tank so i cant figure out a way to create a refugium and i would rather not section off a part of my tank to plant it.  My question is what can i do besides letting algae take over my tank to reduce these nitrate levels.  I also have been doing 50% bi weekly changes.  Thank you for your time.

Answer
To get things back in order right away, replace 25% of the water every day for the next 3 to 5 days. Vacuum the gravel well. If there is crud down there the nitrates will never stay low. The beneficial bacteria is doing it's job by consuming the waste, but the bacteria's waste product is nitrate. So, too much waste leads to too much nitrate. Once you have done water changes for 3 to 5 days, do a regular maintenance change of 25% every week from then on. It's really necessary to keep the water conditions stable. This will keep the nitrate levels down naturally and keep the fish feeling healthy.