This is BBA - isn't it? :(

[tyella]

I'm not an expert, so I don't want to jump in over my head (required caveat) ...but:
I think of Java ferns and Anubias as being rather slow growing. Aside from those, you have only a banana, a sword and a crypt in a 42 gallon.
I humbly suggest (and hopefully others will correct or confer) that you add some fast growing plants as soon as possible. You can put in something cheap that you can swap out later. I'm doing this with Hornwort in my tank right now.

 

[djlen]

The BBA will turn gray or white after dipping and should disintegrate gradually, as time goes on.
You can raise your kH with baking soda immediately and gradually with crushed coral
in the filter for the long term.
Does your N=20 out of the tap or haven't you checked that? Any P coming out of the tap?
You have a low light situation with low light plants and IMO, will not need a lot of dosing to keep them happy, however if your tap is supplying 20ppm, N you should balance that with a bit of P and K. Traces is also a good idea @ 1/4 strength and Fe is not necessary at this time, IMO. Extra Fe can cause algae issues if not used by the plants. And you are supplying some in the trace mix.
Go very lightly with all nutrients and observe the plants for signs of need. You want to get them growing, but not over-fed.
I would try dosing 3 mls. per 10 gals. of Excel daily and see what effect it has on the BBA.
You should work on improving your kH if you're going to continue injecting CO2.

Len

 

[illiswiller]

Thanks Len and TY

So I'm really confused now about the KH - I'd posted before about raising KH - (b/c my pH kept dropping w/ the CO2).....and I thought the aragonite would raise the KH (but it hasn't)....Everything I read online said to use Aragonite OR crushed coral...I figured they were interchangeable?? Is that not so? So would I need both in the filter?

I haven't tested for P, N, K or Fe....haven't gotten tests for it. My local LFS doesn't have one and I couldn't find it at Petsmart. Can you recommend a kit online? I'll do the prescribed Excel at 3ml / 10 gallon and watch.

Yes, maybe some faster growing plants would be helpful. Problem is most of the fast-growers seem like they need more light than I have to offer.... I'll search through the forums for some recommendations...