Wow thats some explosive growth. Doesn't all those emersed growth take away too much light?
Yeah it does take some, especially when its that overgrown, but this tank has taught me how very low the light can go, and plants are still perfectly fine. Most of the plants are low light types - ferns, crypts, anubias, buce etc, and they seem to do fine at light levels far lower that most of us would expect.
Did you introduce the duckweed on purpose
Lol Nooooo, it's my nemesis! I had in my previous tanks, so I went to huge lengths washing and cleaning all the plants I transferred into this tank to avoid it coming back. I went six months duckweed free - it was glorious! Then I moved a couple of crypts from another tank that had some duckweed in, and although I rinsed them, I wasn't as methodical about it. Two months later, duckweed! It's plagued me ever since. Several times, I removed every visible trace of it, but with all the emersed growth it's impossible to get rid of every single bit, so it just comes back over time. It's due another cull as you can see.
What is your ferts dosage as I may ask?
Micros and macros are dosed daily a couple of hours apart. Weekly I dose about 10ppm NO3 and, 1.5ppm PO4 from KNO3 and KH2PO4 respectively, which then also results in about 7pppm K. On the micros I dose about 0.3ppm Iron, from 0.2ppm APFUK mix (so that 0.2ppm as a proxy for all the other micros), and 0.1mm Fe Gluconate.
MgSO4 and CaCl2 get dosed with the daily water change to around 4dGH, which adds around 6ppm Mg, and 18ppm Ca per 50 litre change. TDS sits pretty stable at about 96ppm.