OK, home from work, got my beer.
Snail, if you got him out just go on snail patrol and watch for little ones and pull them out any time you see them, hopefully you got it before it laid eggs. But all snails are not bad news, I actually keep pink pearl ramshorn in my little 7gal tank, their actually a quite beautiful species of snail and only plant they eat is my floating plant which grows out of control anyway. Snail poop is good fertilizer and full of all kinds of beneficial microbes.
On glass top donít completely seal up top, to want gas exchange between water surface and atmosphere. Iíd leave about 1.25Ē on front and back edges. If water starts condensing on underside of glass you need more airgap. Proper air circulation letís ammoniaís escape from aquarium as well as letting water absorb CO2 and oxygen.
Go to hardware store and buy you some fiberglass window screen the cheap stuff, itís about $4-5 for a big roll. Cut you out strips and glue to front and back edges of glass with clear silicone. Itís very easy to cut out around filter or make little notch where power cord for heater goes into tank. If your handy cut a little strip of plastic for along front edge, glue it on and glue on a little handle so you can lift front flap to throw food in. If you want just make front flap 2Ē wide for easier access when feeding.
That same window screen material you can roll it up in a tube 3 layers thick, glues it shut along back and bottom and make strainer sock that will fit over input tube of Aquaclear to keep shrimp from getting stuck to input.
Hornwort, Iím like meh. It not for me, itís messy. Me Iíd rather have my small colony of red root floaters. A OMG no to duck weed, thatís the herpes of floating plants. Hereís red root floater from top, little 1cm sized leave on a mini vine. Note little float ring I built to keep it out filter down pour area and where I want it. I have exact same light as you and exact same filter, just on a 7gal bow front tank. Itís perfect sized floater in little tanks like ours.
Here you can see it from side with nice blood red roots hanging down. Itís actually redder than that photo looks, white betta always screws with white balance of photo when heís in shot. Also youíll see little pink ramshorn that I keep.
The other plant you see there is rotala rotundifolia and thats what I mean by a stem plant. Your swords and crypt plants are crown plants, crown at base/substrate level and leaves come up from that point. Anubis are rhizome plants, kind of a vine that needs to be kept above gravel or attached to wood/rock and creeps along from there sending up leaves as it goes. Now that youíve moved heater and input tube to filter you might consider a stem plant in front of those. The crypt youíve got back there now might not grow in as tall as you think afternoon few months. Your nicrew light is actually pretty good med powered light at 9Ēish depth of your tank, crypt when grown in stronger light tend to grow shorter and more squat rosettes, put exact same plant in dimmer light leaves will grow more elongated.
A small clusters of longer stem plants along back wall between sword on left and heater/intake tube might look pretty good and give you some balance to design. Different textures, different colors make tank more interesting
Some rotala indica doing itís pretty in pink thing as it grows closer to surface and gets more light.
Iíve got some of this ludwigia super red mini in my quarantine tub downstairs dealing with pest snail problem that Iíll be adding to my tank once I get through that problem.
In my little 7gal I donít do CO2 but I wouldnít dissuade you from doing it, no doubt it can accelerate grow and provide vibrancy to tanks health. But Iím all low tech/low maintenance these days and donít want to deal with that kind of tech anymore.
Got to go, iPad battery running down and donít want to lose all this typing.