Nice start, too bad you've had a few rough patches. I'd say you could def try for some fauna in here again, but take it much slower; you seem to be rushing things quite a bit. First have this bowl up and running WITHOUT changing anything around- moving bowls, adding co2 etc- so it has a chance to fully stabilize and the plants become well established. Aim for the bowl to have crystal clear water (it will happen) and for the plant growth to look like an overgrown jungle before you put any live animals in (should take at least a few months). Then when you do add livestock, go low and slow. I'm not surprised you lost the original two shrimp, adding 10 at once in 4" of water in an uncycled system is bound to create problems. Try adding about two or three shrimp at a time, then waiting a week before deciding to add more or not- or better yet, just let them breed on their own to get more. Don't plan on feeding anything you have too often; when it's established, the shrimp should get enough food from algae and other pickings that they need to sustain themselves, with maybe a very, VERY small supplemental feeding once a week or less, which should be gone in a matter of minutes; not only will the (smallest amounts of) uneaten food create major problems, but you must also take into consideration the waste the shrimp will produce when they pass the food, and whether your plants will be able to handle that. The objective is to add in as little outside organics into this system as possible which could cause water quality to become ill. Good move on the duckweed, that's great for sucking nitrates and other nasties that come with a new system, but make sure you remove it before it gets so overgrown that layers form and the bottom starts decomposing. I'd recommend that you steer away from fish unless you've had experience with this type of setup before, or you go for an air-breather (betta is your most likely solution), but be prepared to siphon detriusfrom the bottom with regular water changes if you do. (my fish recommendation otherwise would be a single Heterodon formosa). C02 is a no-no for this type of system, and you may want to consider setting a desk lamp on it (not one that will get too hot) to increase the plants' photosynthetic rates, which will result in higher oxygen output. But I totally agree; before this progresses any further, a test kit is the way to go! don't get discouraged and don't give up, the one thing that these things take is patience.