Stocking 30 gallon aquarium?

You have do have some room to add more fish.

However if you want to see your WCCMs and neon tetras really happy, you add more of the same species. 5 is the minimum limit, but you have plenty of room so no need to stick to the minimum numbers. Schooling fish do best in large groups.

Even if you bump up the numbers of your current fish to 8-7 / species you'll still have room add more fish. Recommended fish:

Dwarf gouramis do best alone. Depending on where you live, female DGs are a rare sight, or non-existent at all: stores tend to stock males, as they are very very pretty. So the general rule is 1 / tank, no mixing gourami species.

Honey gouramis might work too. They do best in 1M, 2-3F groups. They are smaller and more peaceful than DGs, and often more shy as well. The good news is that stores stock mixed sex groups the bad news is that golden gouramis, thick lipped gouramis sometimes get mislabeled as honey gouramis.

You could also consider adding live bearers, 3 male guppies or 3 male platies would do well in a 30 gallon tank.

As for other creatures, I recommend nerite snails. They stay small, they are very pretty and they are exceptionally good algae eaters.

Mystery snails get surprisingly large. They also need supplement feeding of veggies. They are fun to watch, definitely conversation starter snails, however their size, appetite and waste producing can limit your stocking options.

" Cloud minnows usually need colder water, rather than the warm water tetras need, so I'm not sure on how long they will last."

Their temperature range overlaps (16-22°C for WCCM, and 20°C-24°C for neon tetras) however temperate fish tend to do better with seasonal changes of temperature.

"Even add a few pigmy corydoras, they will help keep your bottom clean, and look really good."

The problems with these is, that the smaller the schooling fish is, the larger group you need to make them feel safe. So it's either 10-12 Pygmy Cories or no Pygmy Cories at all.

As far as Cories go, I recommend Panda Cories. Larger, more robust than Pygmy Cories but still on the small side with their 2 inches length. Get minimum 5 of them. Cories need their own food, which is not algae btw. Cories are omnivores, they do best on a varied diet of sinking catfish pellets, frozen or live foods and some leftovers.

You wouldn't be overstocked. You've got some room, especially since neons and cloud minnows don't take up much space at all. Cloud minnows usually need colder water, rather than the warm water tetras need, so I'm not sure on how long they will last. I can recommend a dwarf gourami, or even a few as good centerpiece fish. They are bigger than the fish you have now and are hardy. Also look beautiful and will balance out your big>small ratio. I can also recommend some Molly's, they come in some beautiful colors and look great. Even add a few pigmy corydoras, they will help keep your bottom clean, and look really good. I would definitely do the corys, and choose either a few Molly's or a few Gouramis. Good luck!

You still have a decent amount of space. Corydoras (for example, albunos) would be lovely for your tank. They have to be kept in groups of at least 3, so you could have up to 6-7, depending how long your tank is.

Or, you could have shrimp. For example, ghost shrimp or cherry shrimp would be great. They can be kept alone, or you could have even 10-15.

Also, on top of either of these combos, you could look into buying a mystery snail. It seems like you're just looking for some more flair for your tank, and these snails can have very cool shells. And, they will travel all through out your tank!!

Guppies, Neons, Zebra Danio, Swordtails are all good fish. Neons and Danios should be in groups of 5-6 and Guppies can be in groups of 3-4.

Consider a max of about 25 fish total in 30 gallons and you will be fine.

If you can find them, Gold Tetras are lovely. They are wild caught, so it would be a good idea to quarantine them. They have really incredible coloring.

Another option are Rummy-nose Tetras. These are one of the tightest schooling Tetras you can get, and will school as a unit in open water.

For lower water fish, Corydoras Catfish are good. They need groups of at least 4. Kuhli Loaches are another possibility, they need groups of at least 5.