tips on lowering high nitrate levels

[burrows14]

the tank is almost 3 months old , its went thru its cycle before i put anything into it. i do a 25% water change every 2 weeks but i did one last thursday and one this thursday trying to drop this nitrates. i have a lil cyano growth but very minimal and since i started the tank ive always used reefchem stabilllity. i test my water every thursday and have never had any chemistry problems at all.