Looks great to me. I get your concern over BBA personally still not convinced its the substrate but that sure doesn't mean it isn't.
hmm If not the substrate what else can it be? This tank is very mature like 6-7 years, equipment wise it has gone from:
1 Ehiem 2217 -> 1 Ehiem 2213+2217 -> 2x Eheim 2217 -> Fluval 406 + Ehiem 2217 - Flow wise I think it's more then enough it's only a 40g breeder
Canister filters are cleared every 4 months, but lately I been cleaning every month to 2 months due to BBA and organics.
Lights has remain the same Odyssea quad T5HO, bulbs changed every 8 months to 1 year always 6500k, just yesterday I decided to change 1 bulb out for a Geissman Super Flora
Substrate has always been 2.5 bags of Netlea Brown plant soil, I orginally bought this soil with the intent to breed CRS but realized the tank is way to big and I won't see any of the shrimp
Heater has gone from Rena 200w -> 300w -> Ehiem Jager 150w
Co2 has always been Milwalkee regulator and the diffusers I gone from Rinox Glass diffuser -> Up aqua inline mister -> the green one with bioballs -> istal max mix -> Jaqno Co2 Reactor -> Back to up aqua inline mister -> diy Cerges co2 Reactor
Fertz has mostly been PPS pro (old formula with the micros being dose 1ml per 10g instead of the new 0.1 per 10g), I did try EI dry dosing for a few months but didn't like to do big water changes, since I have like 7 other tanks to take care of.
Feeding has always been the same I feed once a day on monday, wednesday, and friday.
I find that I get an outbreak of BBA whenever I uproot plants to sell. Because of this though I decided to do a tear down a month ago and I gravel vac the substrate which is like impossible because it's soil base and just creates a mess. Took like 3-4 days for the tank to clear up, I even added 2 filters stuff with filter floss making it 4 filters to clear up the tank faster.
This is what the tank looks like at it's peek in 2013, Cardinals I started off with 60 or so they should be 6 years old now and I have 6 left out of the 60, harlequin tetras I started off with 40 and they all died maybe last year or so.
tank in 2013