EChord
Aspiring Aquascaper
I totally understand. You should see some of my very first shots - the learning curve you go through is always big. The fact is, you've already learned some excellent composition and angles, so you're ahead of the game. 
You might want to check and see if there's a photo group in your area that you can join. That helped me learn a lot, since ppl would put shots up for critique. Hearing that critique on various shots, whether mine or other people's was tremendously educational.
Here's some more info just in case. I don't know how much you do/don't know, and I remember how much I had to learn, so I figured I'd touch on a couple key items.
ISO
Typically you want the ISO as low as possible, since you tend to get more noise at a higher number. That being said, the higher the ISO number, the less light the exposure needs. You'll have to play with your camera to see at what point the noise becomes too noticable in the shot. For example, I almost always shoot at ISO 100 (as low as my camera goes), and when I do raise it, I pretty much never go above 800, because that is the point the noise becomes bad enough, that I do not consider the shots usable.
Aperture
Aperture Priority Mode is something you also may want to look into, if you haven't already. This basically puts the f-stop (aperture) under your manual control, while the camera automatically sets the shutter speed (full manual mode puts both of those under your control). Typically this is just a question of moving the dial to A or Av, depending on the manufacturer. Aperture essentially controls how wide or closed you have the hole through which the light comes in. The smaller the f-stop number, the wider open the hole is, and the more light comes through. What's crucial about this number, is that the aperture setting affects your depth of field.
Depth of Field
DF (for short), is basically how much distance things can remain in focus within the shot. For example, lets say you are shooting a picture of a river going up into a mountain. For such a shot, you might very well want the entire river, both the foreground a foot or two in front of you, all the way through the back end of the river (maybe a mile away), to be in focus. This requires a high number f-stop to accomplish. This is why landscape shots are typically shot around f/22, which means the hole is closed very small (like a pinprick size).
Now, conversely, let's say we're shooting a macro where we want strong bokeh (blurred background), then we want as shallow a depth of field as possible, while still keeping the subject sharp. For that type of shot, you might want your setting around f/2 or 3 (assuming the lens goes that low). There is a caveat in here as well. When dealing with very shallow DF, you might only have a cm or so that's in focus. That can be a problem if what you're trying to shoot is wider than that, such as some of the plant shots you have. This is why f-stop isn't really a hard and fast rule.
For average everyday shooting, an f-stop around 7 or 8 is usually good and will produce strong shots.
Focus tips
When shooting critters, often times you can get away with having most of their body fuzzy. What's critical to be sharp in focus are their eyes. You have the eyes nice and sharp, the rest is usually fine. When dealing with shallow DF, avoid blurring out your foreground. Background blur (bokeh) is often very desirable, but foreground blur is typically distracting and competes with your subject. There are very rare exceptions to this, and I'll attach one where foreground blur worked, but only because it wasn't a solid blurred area eating up the foreground of the shot. I've also attached a second shot of a blue and gold macaw flying. Note that the wings are blurred, but the face is sharp. As a result, the shot works.
Anyway - hope that all was useful. Again, love your shots!
You might want to check and see if there's a photo group in your area that you can join. That helped me learn a lot, since ppl would put shots up for critique. Hearing that critique on various shots, whether mine or other people's was tremendously educational.
Here's some more info just in case. I don't know how much you do/don't know, and I remember how much I had to learn, so I figured I'd touch on a couple key items.
ISO
Typically you want the ISO as low as possible, since you tend to get more noise at a higher number. That being said, the higher the ISO number, the less light the exposure needs. You'll have to play with your camera to see at what point the noise becomes too noticable in the shot. For example, I almost always shoot at ISO 100 (as low as my camera goes), and when I do raise it, I pretty much never go above 800, because that is the point the noise becomes bad enough, that I do not consider the shots usable.
Aperture
Aperture Priority Mode is something you also may want to look into, if you haven't already. This basically puts the f-stop (aperture) under your manual control, while the camera automatically sets the shutter speed (full manual mode puts both of those under your control). Typically this is just a question of moving the dial to A or Av, depending on the manufacturer. Aperture essentially controls how wide or closed you have the hole through which the light comes in. The smaller the f-stop number, the wider open the hole is, and the more light comes through. What's crucial about this number, is that the aperture setting affects your depth of field.
Depth of Field
DF (for short), is basically how much distance things can remain in focus within the shot. For example, lets say you are shooting a picture of a river going up into a mountain. For such a shot, you might very well want the entire river, both the foreground a foot or two in front of you, all the way through the back end of the river (maybe a mile away), to be in focus. This requires a high number f-stop to accomplish. This is why landscape shots are typically shot around f/22, which means the hole is closed very small (like a pinprick size).
Now, conversely, let's say we're shooting a macro where we want strong bokeh (blurred background), then we want as shallow a depth of field as possible, while still keeping the subject sharp. For that type of shot, you might want your setting around f/2 or 3 (assuming the lens goes that low). There is a caveat in here as well. When dealing with very shallow DF, you might only have a cm or so that's in focus. That can be a problem if what you're trying to shoot is wider than that, such as some of the plant shots you have. This is why f-stop isn't really a hard and fast rule.
For average everyday shooting, an f-stop around 7 or 8 is usually good and will produce strong shots.
Focus tips
When shooting critters, often times you can get away with having most of their body fuzzy. What's critical to be sharp in focus are their eyes. You have the eyes nice and sharp, the rest is usually fine. When dealing with shallow DF, avoid blurring out your foreground. Background blur (bokeh) is often very desirable, but foreground blur is typically distracting and competes with your subject. There are very rare exceptions to this, and I'll attach one where foreground blur worked, but only because it wasn't a solid blurred area eating up the foreground of the shot. I've also attached a second shot of a blue and gold macaw flying. Note that the wings are blurred, but the face is sharp. As a result, the shot works.
Anyway - hope that all was useful. Again, love your shots!
