You will need some acrylic yarn. Most rainbows seem to like dark green and it makes the eggs easier to see than some colors. Get a large book and wrap the yarn in loops around the book. Some rainbows like spawning near the bottom of the tank, some the top and some don't care where as long as they get to spawn. This seems to be dependent on the individual fish, so get a book slightly longer than the tank depth. Make from 50 to 60 wraps around the book. The more wraps, the less likely the eggs will be eaten. But if its too thick sometimes the rainbows will not go in the mop, and end up spawning on the outside of the mop. Again this could lead to egg predation. Most Rainbows aren't too bad on eating their own eggs, but few fish can refuse an easy meal. Take a length of yarn about six inches long and tie tightly around one end of the looped yarn. Cut the loops on opposite side that is tied. Take another loose length of yarn and tie near the first tie point as if you're making a rag doll head. Use the extra yarn length from the first tie to tie around a piece of Styrofoam. Now you have a spawning mop.
On Line Spawning Mop
____ 1st tie
()____ 2nd tie
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