If you keep Malawi cichlids or any cichlid you will know how readily they breed. Having lots of empty tanks for the fry and females is not always practical or affordable. The easiest way is to divide one spare tank into two or three enabling it to house more than one holding female at the same time. You can buy tank dividers to do the job however i find them to expensive and most of them are attached by hooks over the edge making it impossible to use sliding glass trays.
The solution to this I found easy and much cheaper. You can create a tank divider by using plastic canvas (used for cross stitching) and mini suction cups with hooks. Be aware that the plastic canvas comes in different hole sizes, I found 7 to be about right for the job. The plastic canvas can be bought readily very cheap and is easy to cut to size, if you can not get the right size then just buy more pieces and either tie them together or stick them with silicon sealer. You can get a bag of mini suction cups with hooks (usually 50 per bag, size 19mm) from places like eBay for a couple of pounds.
Then all you need to do is cut the plastic canvas to the right size, hook the suction cup hooks through the canvas holes, one in each corner or more if needed, then stick the suction cups into the tank. You might have to change the hole that the hook goes through so that the plastic canvas is supported tight. If you really want to finish it of and give it more stability you can use a black plastic slide binder along the top and bottom.
If like me you need a tank divider to separate larger fish then this is how I made mine.
I purchased a pair of my favourite Aristochromis Christyi but they were much smaller than my original 8 inch female and so I had to partition part of my tank to save them from becoming her lunch. I bought some plastic egg crate plates with a hole size of 1/2 inch. These plates easily connect together and can then be cut to the perfect size. I then purchased some high quality suction cups, the type that have a hole in the top (not a hook) and are used for securing air line. Using small cable ties I tied on 4 suction cups down both sides of the egg crate, I then had my divider.
All of the above items can be purchased cheap enough on eBay and the good thing about these egg crate plates is that they come apart and can be re-used for a different size tank.