As others have noted, saving a spawn in a community tank is almost impossible; sometimes it works, up to some stage anyway.
All catfish are nocturnal, so they will almost always find and eat the eggs, or the shoal of fry should they hatch, during darkness. Leaving the light on is not an option, as I'll come back to. As someone suggested, to guarantee success, remove the parents to a tank on their own, before they again spawn. You could move the eggs (Mikrogeophagus ramirezi will usually lay eggs on a hard surface, though they may use a depression) and artificially tend them, but it is interesting to observe the fish doing all this, and much easier. Just make sure the tank you move them into is not just cycled but established and use water from the present tank for the first fill so the fish are not subjected to differing parameters.
Water changes were mentioned...these should be carried out normally. Depending upon the size of the tank, you can do these with minimal annoyance to the fish by just inserting the hose in the water at one of the front corners and siphoning out the water, then add the fresh conditioned water the same way. Other work inside the tank can wait.
Now to the light...never leave the tank light on 24/7. Aside from the detriment this does to plants and guaranteed algae problems, this is severely stressful on the fish. I have known of cases where the fish came down with ich solely due to the light. There must be a period of total darkness. This is part of the circadian rhythm that all fish and animals have (plants do too in a sense) and throwing it out of whack like this is just asking for highly stressed fish which significantly reduces their immunity and energy, leading to all sorts of problems.
Byron.