This is a discussion on need quick help with anacharis... within the Beginner Planted Aquarium forums, part of the Beginner Freshwater Aquarium category; -->
i just read that anacharis needs to be used sparingly bc it emits oxygen at day but uses it at night...is there a limit ...
All plants respire as do fish and animals, using oxygen and releasing CO2, day and night. But plants also release oxygen during photosynthesis, which can only occur during sufficient light. There should be no issue of oxygen shortage unless CO2 is being added (by diffusion) 24/7.
One thing about Anacharis, though, and that is temperature. This plant prefers temperate rather than tropical temperatures, so it may not do that well. Also, it is a very fast growing plant.