Hi peeps,
first time posting for me, so a newbie with this and discus keeping. Hoping to start very soon (boss allowing!)

My aim is to have a sump filter under the main display tank. I hate cables and tubing visible in the tank. I also love planting and creating a more natural biotope.
Question is this; I read somewhere, you can't run a CO2 diffuser if you have a sump filter. Why not? Also, as the temp's are higher than 'normal' tropical, dissolved O2 in the tank will be more depleted. How do I get more O2 in, without putting in an airstone in the main tank? Can I oxygenate the sump and if so, recommendations, please?

Many thanks