Why am I killing my fish?!!!

tanker

So, are you just plonking them in? If the temperature is different it will shock your fish. If the pH is different, you will shock your fish. You can scoop out a couple of jugs of tank water to have room to float your bag, or you could just put your new fish in a jug (aquarium use only) and gradually add tank water. Take a bit of water out, put a bit of water in.

You'll probably need to do another water change to get your levels down.

I'd rehome the pleco and not get another. 5 gallon isn't big enough to have one. I only got my bristlenose when I got my 250-litre tank.

I've found it easy to maintain tanks with live plants, but I've just got gravel substrate. I'm not attracted to having sand, I like to get my vacuum down there and I'm not sure how I'd clean sand. In a 5 gallon you'd need to get plants that aren't going to take over the whole tank. I started with some java moss tied to a piece of driftwood - easy to remove if you want to. You could add a java fern tied to a piece of driftwood while keeping your plastic plants and see how it does. If it thrives you could consider planting something else in your substrate.

Disadvantages - you've got bits of vegetation to have to clean out (no major drama, IMO). Sometimes the plants can die and make a mess (no major drama, IMO).
Advantages - they help process the fish waste, they look good, the fish like them.

Christople

I have sand and all the doo sits at the top of the sand and I simply get the siphon close enough to were it sucks up the doo and no sand. My siphon doesn't really suck up the sand so i also drag it across the sand and that is the most effecient way.