I have a 50 gallon tank with two clownfish and a lot of caulerpa both on the rocks and in the sand. I use a 50 gallon HOB filter and there is no skimmer or fuge; the caulerpa have done a decent job of exporting nutrients. I have been away from this tank for two years and need to do a big partial water change, in which I'm thinking of stirring up debris in the sand bed to siphon it out. However, I'm concerned that releasing too much debris will spike ammonia and kill the clownfish. How should I clean the sandbed in a way that doesn't cause too much pollution at once?