Are the stalked plants on the left Bacopa? Are the ones greening up on the right Water Wisteria Hygrophila difformis)? Those will continue to grow. If you pinch back budding branches on the Wisteria, it is supposed to grow a little fuller. That will keep them from (in some cases) growing out of the water. Also with both of them, if you take scissors and cut the tops off, those can be planted (gently push a hole in the gravel with a finger, insert the plant and carefully fill the hole in). Your Cory's foraging may knock the new plants loose from time to time. But if you are patient you should get an even nicer grove of them. Sometimes they make good trading material with other hobbyists or perhaps even your shop.

For more on that stuff, Google Aquatic Gardening, though you are probably familiar already with that.

The school of black tetras is relatively a good thing. They chase and interact with each other rather than harassing the guppies. If there was one black tetra, that would be a lot more trouble for the gups.

" kinda am leaning towards sacrifice to the porcelain god"... Actually stomping on it with your heel would be a lot less painful for the guppy that flushing it. That comment is, um, overkill, but flushing, with its attendant forms of temperature and chemical shocks before the fish finally dies, is really nasty. (One article reviewing Finding Nemo suggested the movie should be called Grinding Nemo, because if he survived the variety of chemical shocks on the way to the sewerage plant, he would then be run through a kind of giant hamburger grinder at the plant.

(I would try increasing the frequency and amount of your partial water changes first - that guppy may just have a problem with something in the water.) If it is necessary to euthanize a fish which can no longer care for itself and is in great pain or is a disease threat to others, try helema23's two tabs of extra strength Alkaseltzer  with the aspirin or the little bit of cold water outside or a suggestion from the euthanasia thread in Immediate Help.  

You mentioned "an xray fish or something like that". You would do well to find out what it is. While it probably will not grow up to feed on guppies, you certainly need to know what you are putting into your tank. Is it a schooling fish? Does it need others of its kind to live a healthy life and to behave normally? What water chemistry and temperature is best for it? Is that similar to that of guppies? What does it eat? How big does it get?

All of us who have been in the hobby have a story we can tell on ourselves or a family member or an acquaintance where a cute little fish was purchased and, whoa boy! did that lead to adventures and/or trouble. ;)

Albino Corys, like all Corydoras, are schooling fishes much like your black tetras. Singly they aren't a threat to guppies, but with company it will be much more animated and "happy."

I'm pretty sure that you are aware of the need for flakes, defrosted and previously rinsed foods or even the occasional feeding of live food to regularly sink to the level of the Cory. Too many really new aquarists think that they eat the droppings of other fish. In nature they eat fish eggs, insect larvae, worms and the like. (Very few flakes fall on the Amazon basin.) If they are actually eating fish feces, they are probably already so desperately starved that they will die anyway.

Feeding bottom feeders is always a little tricky. (Maybe it is more of an art than a science.) Our conventional wisdom is to feed what the guppies can 100% clean up in a couple of minutes. If they do that, the catfish die. If there is an explosive grow of snails (hitchhikers on plants) we get mad at the snails. And of course it is not the snails' fault. They are just eating the food which we are over generously supplying our guppies and company. Snail poop is safer in an aquarium than rotting fish food. In fact, if we didn't have the snails struggling to keep up with our overfeeding, we might be faced with epic ammonia spikes and/or bacterial explosions or all sorts of disease outbreaks because on the one hand the garbage in the water is feeding the few pathogens in the water (and making them millions of pathogens) and on the other hand the garbage is crippling the immune systems of our fish. I can hear the Inkmaker chanting "Change as much water as often as you can!" ;)

I think you probably knew that stuff in the last couple of paragraphs, but it has been a little while since that has been said here. And I feel better for the mini-rant. ;)

It is fun watching the progress of your tank. I'll bet a lot of us can identify with how you are building it as cash becomes available. You seem to have developed a pretty good plan and progression for adding facets to the whole. Keep up the good work and thanks for sharing!