Ok, well I hope next time it will go better. From what you say, I can't really see anything you're doing wrong. After a while though you will be able to tell when they are about to lay eggs, I've actually video-taped mine spawning. Try and catch them "in the act". Also, in terms of slate, it is very usefull to have them lay eggs on a rock so that you can take the rock out and put the eggs in other tank if you want. I've used a piece of "Tile" before, you know ceramic tile etc. You might want to try that. Also that mag. 350 is also pretty powerful, I'd turn it off if they're about to get down to "business". Guess it depends on how it positioned though. Good luck,
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Joe
www.cichlidfish.com