I have a problem I think most people in this hobby wish they had; not enough nitrates!
My tank is cycled, and established. I use API liquid test kits and I have multiple tanks so I know the tests are reading accurately.
The tank is 8.5G with about 5 gallons of water in it, I only have a Betta and 5 Amano shrimp, so the bio-load is rather light. I do a 50% water change once a week, I dose Excel daily and Flourish twice a week. After my cycling period, I have never detected a single trace of Ammonia, Nirtite, or Nitrates! The only time I can get an Ammonia reading is right after vacuuming when the tank is a bit kicked up, even then it is less than 0.25ppm which does not even last long before dropping to 0ppm.
This is not necessarily a problem until recently I can not seem to keep my Frogbit thriving, they are having a real hard time producing green growth it is mostly bleached and now the leaves are not getting big the floating plants are becoming stemmy.
I have two ideas on why this is, one is obviously just not enough bio-load since my plant load is so heavy and I add more plants every week! The other is just another side of the same table, this is a riparium and so it has lots of emerged plants with tons of access to CO2 in the air plus they are closest to the light. I believe the terrestrial plants eat more nitrates then my submerged plants do, particularly the grass in the back right corner I got from a pond the root system is massive and requires weekly trim back.
Dosing more Flourish is not going to solve a nitrate problem though, does anyone literally add nitrates to their water?? I could cut back on water changes but I do not think that will help I still need fresh water and keep my TDS down (not that I check for TDS). I must say of all my tanks this one develops the least amount of algae but it still finds its way onto my glass after a while.