Emily, your tank is looking good. The brown stuff growing in the tank is not cyanobacteria, it is diatoms, they will go away in time. Some Otto's and/or a couple Bristlenose plecos will help clean them up. More plants will also help, you should get some faster growing stem plants like Ludwigia, Rotala, Watersprite, as these will help with the uptake of nutrients as the tank matures and stabilizes.
You don't "need" CO2 injection to grow plants. It does help, but it also has other components that it "needs" to work properly. Higher light, fert dosing regimes, and such. As a result, it means more maintenance, more frequent trimming of plants, more diligence at watching tank parameters. I'm not saying it's a bad thing, but it's not needed to have nice tank full of beautiful plants. I have several large tanks with lots of plants using the low tech methods and I like the way they are.
As for how your plants are doing now, let them grow. New growth is a good sign, it means the plants are acclimating well to their new home. Add more plants.
I like your fish selection too. I would add to the list: 6 cory cats , the above mentioned ottos or bristlenose, possibly a small school of zebra danios. With that you would have all areas of the tank covered, top, middle, bottom, and a cleanup crew. Your center piece fish would be the Electric blue rams, but know that rams tend to be short lived(1-3yrs). The rest of the fish on the list can live for upwards of 10 yrs or more depending on how healthy they are. I have some Phantom tetras (basically the black version of your red minors) that have been in my 125g tank for almost 12 yrs now.
125g makeover ,2x75g, 55g, 40g breeder, 29g, 2x10g, 100g stock pond..........MTS ? Nahhhhhh Just acquired a 150g tall and a 30g long
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