I can explain the nitrogen cycle better since noone really did lol and sice you have live plants which is awesome however ..its not good to add a lot of plants at once kinda like you wouldnt add 20 fish at once you wouldnt add 40 plants at once either ...indeed there are advantages to the staggered approach. the overall display should be the result of a build-up of plants that become gradually established. ANYWAYS lol Plants convert light, co2 and nutrients into biological matter > plant material and foods are consumed by fish > fish waste is excreted directly and indirectly as ammonia ( thats the bad stuff lol) highly toxic! > soooooooooo nitrosomonas bacteria in the filter and aquarium subtrate use oxygen to break down ammonia into nitrites > nitrobacter bacteria in the filter and subtrate break down nitrites into nitrates > nirates are only toxic at high levels and are partially taken up by plants as a source of nutrients> the majority of nitates are removed by water changes although some are converted by subtrate bacteria. and it takes more then a few days for the bacteria to get established prob 4-6 weeks but keep testing your water you should always wait the longest you can before adding fish min a week !!! keep testing every few days and only add a few fish at a time obv/ since you already have some which is cool i love those tetras i have some as well :) just make sure that ammonia gets to 0 before you add anything else :)
so Ph is 7.8 . do you know what the hardness is and the acidity/alkalinity is? because that affects plants
what lighting do you have? very important
do you have a CO2 canister??
do u plan of putting liqid fertilizer in every week or so?
what filter do you have? cuz if carbon in the filter is not needed that often in plated tanks as it takes out the GOOD nutrients as well as that bad stuff..
how deep is the tank? there are SOOO many factors lol i would just like to know so i can help better :)