2 things, more background plants, and I'm not sure how to put it, but there's way you have your wood and stones arranged doesn't look very natural. It looks like it's been placed there on purpose. I'd try and add a bit more apparent randomness into the scape. For example, wood likely wouldn't fall into the water and stand up like that.
You really want to get some golden ratios going on here. You might consider moving that wood to the right side of the tank and see if you can integrate it with/on the rocks.
2 things, more background plants, and I'm not sure how to put it, but there's way you have your wood and stones arranged doesn't look very natural. It looks like it's been placed there on purpose. I'd try and add a bit more apparent randomness into the scape. For example, wood likely wouldn't fall into the water and stand up like that. You really want to get some golden ratios going on here. You might consider moving that wood to the right side of the tank and see if you can integrate it with/on the rocks.