I need to see what else I can find for a LFS. Maybe see if they can do anything as far as giving me a little of their seeded filter media or something.
Personally I would never take "dirty" gravel or filter media from a store to use in my tank. Using substrate or filter media from one of your own tanks is fine as you know the state of the tank health. You have no idea what pathogens may be living in this material from a store. And most stores have circulating systems which means disease in any tank in the system can be present even if unnoticed in all the connected tanks. I do not recommend this practice.
As for the biological supplements, there is varying opinions among aquarists, and that's fine. If the stuff is inactive, it will do no harm. If it is live bacteria, it will help seed the aquarium, and more safely than using gravel as above. It's your decision. Here is a link to Dr. Timothy Hovanec's paper on this, he invented the live bacteria in a bottle, and scientifically it is what it says, though shelf life can make it ineffective. Tetra [SafeStart] use his formula, they bought the rights to it; Seachem's Stability is as far as I know much the same, and is live bacteria, guaranteed.
We lost the cory cat this morning. I didn't get a chance to do the 50% water exchange yesterday after work but just did it this morning. That is when I noticed Louie the cory cat floating upside down. I noticed someone mentioned we had a poor choice of fish to have together, can someone elaborate on that? I want more cory cats as I love the little things and I know they should be grouped together in 6 or more. I am not adding fish till this tank is finally cycled. I am going to try and see what live plants I can find to add to the tank also. Anyone have suggestions?
Corydoras are highly sensitive to cycling issues and in fact any water problems, also medications which makes treating them troublesome. I agree, no more fish until the tank is cycled. And plants will certainly help, in this case the fast growing plants (stem plants) even just allowed to float will help; being fast growing they assimilate nutrients faster, including ammonium (ammonia). One bunch of any stem plant floating will help you. Plants for permanent use in the tank we can discuss later, one thing at a time.
You asked about the fish stock. Some of the fish must be kept in groups, the Corydoras and all tetras. For corys, minimum 3 but 5 or more is preferable. Tetras, six is usually considered minimum. All these "shoaling" fish have social structures within their groups and this plus the fact that just being in higher numbers gives them added "security" is important for their long-term health. So any tetra you plan on getting, remember it needs 6 and that takes up space (both physical and water quality). In a 29g, this quickly fills the tank.
The Red tailed Shark should be returned for exchange or credit if the store will; most good stores will because they know we all get ourselves into these problems and they want you to be successful so you will remain a good customer. This fish grows to 5 inches, and if you check our profile you will see several reasons why it is not suitable in a 29g, nor with some of the other fish you have. Profiles can be accessed via the second tab from the left in the blue bar cross the top, or by clicking on the shade name in posts. Please have a look.
The black with white spot "sucker" is probably a plecostomus. Some spotted species reach 12 inches or more. Without knowing which species, I can't say much more, except you should identify the fish and then may have to decide whether or not to keep it.
Different fish require different water parameters. Some are adaptable to some extent, depending upon species, others are not. In general, livebearers (guppy and molly are livebearers) require basic slightly hard water (pH above 7, some mineral hardness). Tetras are the opposite, soft acidic water fish. But many of the common ones are tank raised and adapt to slightly basic water (pH in the low to mid-7's). Your pH is within this range, so it is possible to have a compromise. That can be looked into more when the tank is settled and you are considering new fish.
Many of us, myself included when I started out, go into the fish stores and we see all these fish and assume they basically live together (and sometimes store people tell us so) with no mention made of varying water parameters for long-term health and happiness of the fish. Researching any fish before you buy it is good sense. We have profiles here on many fish, and among our members I'm sure we have experience on every fish out there. I have a habit of never buying fish until I have researched it. Only the other day I was in one of my reliable stores and saw some loaches I had never seen before. They were about 1.5 inches long, seemed to get along fine together, quite attractive. The "common" name on the tank meant nothing (it usually doesn't) so I asked the staff for the scientific name from the supplier's sheet and when I got home I looked it up. The loach attains 5 inches, is quite territorial and aggressive to its own, and doesn't like other bottom fish. Had I listened to the store person, I would probably have bought 3 of them. There's no way I want that in my tank, with my other loaches.