So, for a 4g tank you would be good with a Betta, and a Snail
See how your betta reacts to it, If he nips at the shell, or is constantly flaring at it - then he would not be a very good "Community" fish - so i would not add him to a future 55g tank. The snail will help with Algae upkeep. Before Algae has started to grow, you can get these Bottom sinking pellets (I believe they're called algae pellets), but not 100% on the name - they're the green ones haha.
That's about it for the 4g. Most small fish require 5-7 of the same species to be kept happy. They're schooling fish, and like having buddies.
So for the 8g, you could keep 5 of these (Single species only)
Small tetras (Neon tetras), Danios (Celestial pearls, or Glo-fish), Guppies (Keep either only males, or only females - they will breed like crazy), Also another version of Guppies are called Endlers - they're much smaller than normal guppies - you could fun 6-7 males in there.
As for Algae upkeep (added to the 5 fish you already have in the tank) i'd suggest getting a Snail or two (One mystery snail, or two Nerite snails), or you could go the Shrimp route and get a few cherry or Amano shrimp (The added bonus of shrimp is that they will also eat the leftover food), or a single Otocinclus Catfish (otto cat).
(I'm trying to stick with fish i've seen at name brand pet stores, and not specialty stores i frequent)
If you do have access to a Specialty store, they are more equipped, and far more Knowledgeable than a name brand pet store employee would be + they'd have access to better quality, and different fish species.
Also, be sure to stock your tank with Plants, Real plants, or silk plants work the best.
As far as the betta goes as well - they enjoy "Hides". Name brand pet stores will have a row with all sorts of different ones. Bettas will get stressed out if they don't have at least one place to hide in.
Personally, when i get Bettas i always get what they call a "Betta Hammock", it's just a fake leaf with a suction cup to stick to the side of your tank. Some bettas will enjoy relaxing there. As they're Labyrinth fish, and also require air - this makes it so they don't have to move much to get a gulp of fresh air. However, you may have to replace it after a few months. there's a metal piece that holds the leaf in place. It's covered, but wear and tear of the tank will eventually remove the metal from its thin plastic sheath - and the betta Can hurt themselves on this. I believe they're around 3 bucks.
As far as shopping at name brand pet stores, as well. Be sure to look for a disease called "Ich", it's the most visible.
When i worked at one we were still REQUIRED to sell sick fish, so long as we made a buck. I never Adhered to those rules, but some do. (Again, this could also just be the store i worked at - others i've been to have been fantastic)
So, Basically Ich shows up as little white spots (They look like Salt flecks up close). If you put a fish with ich in your tank, it will infect the other fish and you will need to medicate.
Here's a picture of Ich on a betta.
Ich will infect the tank, as well as any other tank that uses the same filtration.
Name brand pet stores has columns of tanks. Every 2 columns has the exact same filtration - so if you see fish with ich in any of those tanks, treat it as All of them have it.
Also as another note, My mother and i made this mistake in the past. They had a sale on these fish called "Chinese Algae eaters"
Do not buy one. ever. We were told they wouldn't get big, and that they were super peaceful and yadda yadda.
Yes, when they're younger, and smaller - they are. But they grow- and they get big. Also, when they go get large, they get very territorial and will attack, and kill fish. I Lost a betta to one of them.
Phew - Sorry for the long winded post - But hopefully that helps!
