I agree with little_fish unless the clowns are spawning which yours are not yet. My clowns were spawning for about a year every couple weeks like clockwork. Then they quit for a month. So I went on full research mode trying to figure out why "Wren and Stimpy" (my two clowns) just quit spawning as I had added nothing or moved anything in the tank. All my water parameters were dead on consistant so I was baffled. Then I came across something that intrigued me---It seems that the clowns not only wouldn't like change inside the tank were the eggs are laid but also wouldn't like change to things they could see outside of the tank(i.e. chair, table, lamp). Low and behold a sitting chair had been moved from their line of site from that side of the tank the month before. Put the chair back and eggs were laid two days later. Now was that coincidence, maybe or maybe they didn't like the change. Just thought I would share.