Aww I love fish but I can't understand the ph level things or whatever, I don't think I could keep them responsibly. I have a tarantula instead. I also have a rabbit named Mars - a good name!

It's chemistry, basically.
PH is how acidic or alkaline the water is. Too much ether way and it's bad for the fish.
The main problem people have are Ammonia levels and the nitrogen cycle. Wild fish don't have this problem to nearly as much because rivers are constantly pushing new water through and waste is being pushed away and not having time to degrade and stank up one place.
Chemicals are put in our water to remove all bacteria, and there's chlorine present to keep it clean so nothing grows in it. Good for us, bad for fish. There's no bacteria colony in the water which is needed in order to naturally get rid of the ammonia. Plus chlorine burns. When setting up a new tank you must give it a month for this bacteria to establish otherwise you're putting fish into an enviroment that doesn't have any way to get rid of the ammonia yet, often causing a spike in it which can kill the fish because they're breathing in their own festering waste. And, because the waste is sitting there, there's no where for it to go, it just gets worse and worse. Once the bacteria is established, it will turn ammonia into nitrite, which is also harmful, but then into nitrate which is less so. There is, however, only so much this bacteria can do and you still need to do water changes about once a week. 20% or so, leaving enough of the good bacteria in to keep multiplying and eating the bad stuff.

TL;DR
SCIENCE.

Oh my @w@ This is why I ended up getting a tarantula. Tank, substrate, hiding log, water dish. Toss 2-3 crickets in every 2-3 weeks and that's about it. I've tried really hard to understand the water stuff when I had bettas but like I said I truly couldn't even though I really wanted to and decided it was best for everyone not to take care of an animal I couldn't completely understand how to care for.

That's a really nice offer ;o; I don't think I would as I don't purchase any animals anymore, only would take them from someone who doesn't want them anymore and I wouldn't go out of my way to get any fish due to really not understanding (though I tried really hard) but if I ever end up with some (it happens sometimes, a lot of ppl neglect animals and I end up taking them in and rehoming them) I'll try to reach out for help rater than struggling on my own *v*

I have two! Entirely by chance I got a male and female. The female is much friendlier than this grump ahaa. He immediately dashed off when he noticed I took his picture.
I never dreamed I'd have a tank this big honestly. There used to be one in a burger king I went to as a kid, I always had to sit beside it. Used to always love the 'sucker fish' (now I know it was a common pleco). All this started with a little 10litre tank and my failed attempt to grow triops. I got snails, then upgraded and got fish and.. well, it spired a little out of control bahaha!

We might actually have the same tank if it's a 64 litre haha! That was my first proper tank. My betta also lives in there now too, along with some shrimp. Only tank left in my room, though it's nice to have something to stare at when I'm falling asleep.
Can't get bigger than the 520 though. It was murder getting this thing in the house, it fit just barely through the door and required 4 people minimum to carry it. I don't think it'll ever move from where it's at in the house now ahaha.

I taped a hose pipe to the bath taps and lead it downstairs into the tank bahahaha. Dechlorinated it once the water was in the tank (without fish obv). I managed to cause a leak in the taps, but the tank is full so.. not so bad bahaa.

I had mollies for literally a day. Woke up the next morning and there was poo EVERYWHERE and I hadn't even fed them. Took them back lol I read that they pooped a bit which I was prepared for but literally the entire tank was swimming with feces in 10 hours

Mollies do poop a lot, though for an entire tank to be full of it in 10 hours sounds like you didn't have a tank big enough for the amount of fish or a decent filter. Never had a problem with the champion poopers myself.

I read online and apparently it was sufficient for 2 ;_; The filter was rather small though, I'm glad I brought them back so they could go to a better keeper! Got another betta instead :>

Adult mollies are best with around 20 gallons or more. They get pretty big (shops sell most fish as babies). I can totally see anything smaller than that getting dirty real quick. I had one of my girls in a 10g sick tank and she was miserable. Defo too small to be permanent. I will say tho, good on you for letting someone else have 'em.

cuties!!
i wish i could get more into fishkeeping, i just have a betta for now in a 3 gal. yours are so pretty!!