Originally Posted by pettygil
I ask because my fish keep dying and I wanted to see which fish would last the longest. If fish are hardy they would last longer.
Sorry, but if the fish were cared for properly from the start they would last longer. None of your fish would be considered " hardy" if you compared them to the truly hardy " you can drop them on the floor, kick them down the hall, drop them again while trying to bring them back to the tank and they suffer no issues when returned to the water" species of fish. Those fish have a lifespan of 10 - 15+ year lifespans and wouldn't fit in a 20 gallon tank. ( Your Red Eyes have a 5 year lifespan.) Tetras in general are more fragile but you are not dealing with "natural" tetras with the Glo fish and the Red Eyes ( Moenkhausia species) are a hardier variety of Tetras. Some Cory catfish have 10- 15 year lifespans while others barely make it to 5 years. ( Your varieties fall into the latter category. ) It all depends on the species. Even your Bettas only have a 2-5 years expected lifespan and they come from a family of fish that are designed with the ability to live in really poor low oxygen water. Keep in mind that the lifespan starts when the fish hatch or are born and you have no idea how old they are when you get them.
This is why people who breed fish so they they can keep a certain strain of fish in the fish tank have fish for longer because they know they are getting the maximum lifespan.
The issue ( I believe) you are suffering from is that your fish are going through the after effects of being in the tank while it was cycling. That does shorten the lifespan of many species. Add to that that you mixed fish of different sizes into a school ( a non natural occurrence) where the larger fish may be stressing the smaller older fish. This is the problem when you don't see what you are buying before you buy them.
If you had a store you could go to and saw that all they had were larger Red eyes than yours already in the tank, the right move would have been to not get those.
Fish keeping is a learning process. I'm not sure anyone has ever had a 100% successful first tank. Sadly, I've found that people today are not given ALL the information really required at the start to keep successful tanks. ( Look how many used tanks are for sale by people who tried once, failed and gave up.
) For us old people who have been in the hobby for many years, that took reading many books, going to fish keeping groups, experimenting on different things and a lot of trial and error and lost fish. That's just the nature of the hobby. Add to that that many of today's fish are the product of mass breeding rather than the taking of the more hardy wild fish. I've seen more deformed and unhealthy looking fish in stores today then every before. You don't get as many of them when you breed a single pair.
The upside of keeping fish is that when you have a good tank, they are a very soothing, calming thing to watch. Fish have different personalities that you only really get to see when you sit and watch them for hours.
The downside of keeping living organisms as pets and that includes plants, fish, dogs, cats monkeys, birds, humans, etc is that there are no guarantees that they will live or live for long. You hear about people who have " brown thumbs" and can't keep plants alive yet others with " green thumbs" have no issues with the exact same plant. What's the difference? Sometimes it has nothing to do with the plant or the person. It has has to do with the care and environment they are kept. Some people can keep very fragile fish with no issues and others kill very hardy fish. Some fish only live 1 year ( they are called annuals) so you get them with the expectation that they are not going to last long. The best you can do is give your pet(s) the best environment to live in. When it comes to fish, that doesn't happen overnight, even with all the new products and techniques available.
What I will tell you is that with fish tanks, if the water is good, the maintenance is routine and consistent, the feed is top quality but the mix of fish is off, the tank will eventually level off to the proper balance. The stronger fish will eventually outlast the weaker ones.
You just have to understand that you will lose some of the fish when that happens.
It might help you to go to a public library and get some books on fish keeping to read or find some kindle books ( if that's your " thing
) and read up on what it takes to keep a successful aquarium. Every piece of information you can get will help you in the long run.
#1 is the actual aquarium. #2 is mixing the right fish together in the right sized tank. ( Not every species that mixes together will mix together in a small area but will in a big area.)
Hope some of this helps.