How Many/What Fish can I Put in my 20g Cube Tank?

[Slash-GNR]

Hello! I am new to this forum and also the saltwater aquarium hobby in general. I have only kept a couple of Betta fish in the past that have lived out full lives, and now I want to graduate to saltwater. I have done a lot of research regarding saltwater nano tanks, and have read that 3-4 small fish can be kept in a 20g. I wanted to get other people's thoughts on this? I also want to add beginner coral in the future (I want to be sure I can keep fish alive and well for a little bit with just live rock.) If I do that, how long should I wait before i put my first coral frags in the tank? And will this affect how many fish I can keep in the tank?

 

For the fish, I know I want a pair of clownfish. Anymore suggestions?

 

I apologize if I am slow to understand. I'm still learning, so please have patience with me.

 

Thank you!

[Tired]

3-4 small fish is reasonable, yes. I would recommend only 3 unless one of them is a very small fish, like a clown goby. 

A shrimpgoby/watchman goby and a pistol shrimp make for an amazing symbiotic relationship to watch, will stay out of the clowns' way to avoid aggression issues, and are entirely suitable for a nano tank. Pick one of the smaller gobies, preferably, something in the 3" range. A tiger or candycane pistol shrimp is a good match.

If you had two clowns (get the "nemo" variety, in any color variation you want) and a small shrimpgoby, you could add a clown goby as your third fish. They taste bad, so clownfish won't nip them, and they perch up on the rock where they won't bother the shrimpgoby. A neon goby is another candidate. Or you could not have a fourth fish for awhile, make sure the tank can handle three like it ought to.

 

Amount of coral you have in the tank doesn't really matter as far as bioload, with the possible exception of a lot of anemones (not technically coral, but the same idea as far as care) or a tank jam-packed with coral to an absurd degree. They don't have the same kind of metabolism as fish.

 

You can add easy beginner corals at any point after the tank is fully cycled. Waiting a month or so after other life is a decent idea, though. Zoanthids and palythoas are good starters, though be aware that some, especially palythoas, are toxic. It's not a huge concern, you just shouldn't touch them with your bare hands, should be very careful not to cut yourself while fragging them, and shouldn't boil them, scrub them with steel wool, or anything else destructive that would put particles into the air. Pretty much the same safety precautions you'd take with any coral or live rock. 

Green star polyps are cool, but spread like mad. Those are best isolated on their own rock, or kept out of your tank. Same for xenia. 

Avoid anything other than soft corals at first. Once the tank has been up for a few months and is starting to be established, you could try something like an acan lord or blasto- those are pretty, fairly hardy, and not aggressive stingers.

 

Get yourself a pair of long, rustproofed tweezers. You'll like those for moving frags around. Also, get a good turkey baster.

 

Expect lots of algae at first. It's fine and normal. Leave it alone unless it's smothering something that can't avoid it, and let the tank figure out its balance, with cleanup crew and manual removal adjusted as needed. 

 

If you want hermit crabs, get scarlet reef hermits, they're the least troublesome. Make sure they have lots of empty shells to change into or they'll kill snails for shells- which is fair, they need those shells. Just get a couple, they're more of a fun thing than a really effective cleanup crew.