Fighting nitrate

[Ruth]

I have been trying to get my nitrate level down for the past month or so. They have been sitting at about 20ppm on my Sailfert test. They would lower somewhat when I did a water change but always climb back up again rapidly. I change about 15% of my water every 2 weeks and had been going to every week to try and get them down. I cut back on feeding and none of this was having any effect. Well yesterday morning I pulled out the big sponges that are in my fuge/sump - I have always taken them out and rinsed them when I do water changes and put them back. Well yesterday I just left them out and also ran carbon with a Magnum 350 for 24 hours. Today my nitrates test at about 2 plus ppm. Amazing - those sponges I think were my problem. Will have to monitor but the sponges are staying out!