Ahab here, recently with the tank my group has been having trouble with high ammonia levels. We have been changing the water and everything but the ammonia levels would still not go down. So today I had to siphon the gravel, which was not a very enjoyable task. You do this so left over food and fish poop that has settled into the gravel is cleaned out, since stuff like that contributes to the ammonia level in a tank. The task is not enjoyable because you have to start the siphon by sucking the water out yourself, this can often lead to you getting a taste of fish water, not very pleasant. It will all be worth it though if we can bring our ammonia level down.