I would change filter socks out every 3rd day. Remove sand completely. Test tap water for ammonia, if that checks out I would be doing 80% changes Daily. Move some of the lava rock around in your sump and look for waste built up. I would also add some airstones within the lava rock and think of getting some better media.
What would removing the sand do? What if my tap water has ammonia? I thought lava rock was one of the best to use because of how manipulable and porous it was? Sorry for my twenty questions, I'm just trying to learn and grasp what and why I would be doing these things.