The Much Used "is This Too Many Fish?" Question

[Rynofasho]

I have a 36 US Gallon tank with an Aquaclear 50 filter. The tank is pretty heavily planted, been running for probably 6 months, and is fully cycled.

Currently we have the following fish:

5 Long Finned Zebra Danios
8 Lambchop Rasbora
8 Peppered Cory Catfish
2 Bristlenose Plecs
1 Male Betta Splendens

So we went to the petshop the other night and now my wife just has to have some Cardinal Tetras. I explained to her that we are pretty fully stocked and that we'd probably need to buy at least 6-8 Cardinals for them to feel comfortable so that might be too much, to which she replied "Go ask your fish forum friends" hahaha.

That said, here I am! I could rehome the Betta back to his other tank if need be (he already chomped one tail after being in there for a few days), but do you think I would be pushing it if we added 6-8 Cardinals? I could potentially run out and get an AC75 if I absolutely had to or if she were insistent on getting them, but I was wondering what you thought in my tanks current state.

Thanks!

 

[KittyKat]

Assuming the filter is rated for a tank that size, they would fit, but I would recommend that you get another 2 rasboras and 5 zebra danios instead.

 

[Aqua Tom]

How many Cardinals did your wife buy?

 

[Rynofasho]

We didn't get any fish yet. Why would you recommend so many of the others? The 5 Danios are fine, no aggression, and 8 rasboras sounds like plenty to me.

Ideally I'd like to get 8 Cardinals. I change about 10 gallons a week anyhow to get excess plant ferts out.

 

[corinne]

I used to work at a pet shop and the general rule I was taught was 1 fish per gallon of water.

 

[KittyKat]

Why would you recommend so many of the others? The 5 Danios are fine, no aggression, and 8 rasboras sounds like plenty to me.

Because they are schooling fish and all schooling fish do much better in larger groups. I do use 6 as a minimum for recommendations, but in my personal experience, most schooling fish do best in groups of 15-20+. Also larger groups tend to me more impressive, especially once they start breeding.

I used to work at a pet shop and the general rule I was taught was 1 fish per gallon of water.

It's more of a vague guide, than a rule.. it doesn't take into account the set-up details and the species of fish. A 12" oscar doesn't exactly compare to 6 adult cardinals, for example.