Could the additional bicarbonates come from the fish food? It's the KH that seems to change when I add the Thrive C. The GH stays constant at 180ppm and the KH goes up to 80ppm. I'm using CaribSea Peace River for the substrate and it should be inert. There are a few rocks in the tank that I've used to hold the plants down. The rocks are from my Dad's rock collection and are tumbled agates and other silicate materials. All of the rocks have been in the tank for years.
The tank is a make over that I started on July 1. The original set-up had a gravel and laterite substrate and when I originally set up the tank in 2013, the plants grew like weeds. As the years passed, the plants did less and less well until finally all I could grow was jungle val and algae. Over the years I tried everything, more light, different plants, more water changes, fewer water changes and I never could get the plants to grow as they once did. I finally decided to swap out the gravel for the Peace River. When I did the change, I didn't mess with the canister filter and I replanted the jungle val and some apos.
The tank in question is a standard 75gal set up with an Eheim 4+ canister filter, Finnex Ray 2 light, Brand X T-8 light that is used to hide the light leakage from the Finnex (the tank is next to the TV). Tank temperature is, and has always been 78-80F. I am also using an EcoTech wave maker that I recycled from a reef and an auto-fill system, also reused from the reef.
I do a 15% water change every week and I add 1T (about 15ml) of the Thrive C. Just after I added the gravel, I put in a handful of SeaChem plant tabs and situated the tabs under the rooted plants.
I've noticed that in the last few days the plants seem to be picking up and looking a little better. Maybe I'm just impatient?
Here's a picture of the tank BBA and all. I didn't remove the BBA from the sides of the tank because the pleco likes it. She/he leaves tracks in the like a lawn mover through tall grass. The otos also snarf around in the BBA. The pleco is a mistake and I'd like to rehome him/her, however, Patty/Paddy Pleco is my husband's favorite fish and DH won't hear of any re-homing. The are also four clown loaches, 4-6in long, a pictus cat, and a red tail shark in there somewhere. The fish are noticeably more relaxed, if less visible, with lots of plants in the tank. All the fish are about 8years old. I'm good at keeping fish, I need to work on my plant skills!