Sorry, missed this. What I was talking about was artificial embankments, like the kind which line raised railroad tracks. When it's not just dirt, you'll see massive amounts of whatever rock is local and common, and granite is about as common as it gets. Also very common in drainage ditches along roads.
I'm picturing 4-6" blocks from the tracks near my house when I was a kid. Anyway, if budget is at all an issue, don't go buying rocks. That's just silly.
+1 on this, I walk down to my local train track and get a bunch of good looking rocks when I'm setting something up, just not sure if they are inert. I don't have a TDS meter, so yea. They look great though!
Sorry, but you do not have enough plants or hardscape to consider this anything but a completely blank slate. If someone came to me and said "I have black substrate and a school of cardinals, what should I do now?" that would be about where you are now. What kind of a look do you want? Tell us about tanks you like and admire.
FWIW I consider clay pots as functional breeding tank items and not as decor in the sense of the kind of beauty I like. You might be different - you probably are - so tell us what your goals are and give us some guidance. As it is, I'd say some natural hardscape (rocks or wood or both) and lots more plants are starting points. I do like the potential of that substrate with those fish.
+1 to that.
Personally I hate the pots. If you keep them then I just don't like your scape at all. But that shouldn't worry you.
I also totally agree with MABJ. You need stuff that is in scale with the tank. the twigs you had in it are just too small for your tank as it is. They are dwarfed by the volume of the tank. Maybe if you got some rocks you could incorporate them.
My advice is to get some sort of a plan of what you want/like. Look at heaps of tanks and pick things you like about them. Then get your materials organised. Get way more than you need so you have a lot to choose from. Like ppl said earlier, you shouldn't need to buy rocks. you can usually pick up great rocks locally, even in a city.
Personally I wouldn't get too many more plants until you have the hardscape sorted.
I would find some sort of rock that is all the same kind and get lots of them in various sizes and shapes. Make a structure to one side of the tank and incorporate that twig. Once you are happy with the hard scape then think about getting more plants. Your tank is very dimly lit so think about getting moss, Anubias, java ferns and the easy crypts like wendtii.
I think you should have the pots on one side of the tank (the rule of thirds aka 1:1.618 ratio) if you want them to look good.It is kinda intentional at the moment. Also have the dwarf sag close together around the pots to create a dense carpet. In the mean time, look for more plants or rocks. You wont even need rocks if you can get more plants. Some low light stem plants shall create a good back ground behind your focal point which is the pots.
You can increase you lighting period a bit. One t8 bulb won't hurt if you have them around 8-10 That might be better for your plants also.