Wow! I didn't know you were knowledgable in areas other than camears. Now, I understand your DDF name.
The first forum I ever joined was an aquarium forum, so that's the name I kept when I discovered DDF
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I want it to be able to hold at least 7 fish.
First tell me where to go on vacation. I want to see at least 7 things.
My point is, the number of fish is mostly irrelevant. What matters is their size, how big they'll eventually get, how much they poop, etc. etc. You could keep 20 neon tetras in a tank, but that tank may not be able to support a single goldfish.
A 10g may be able to hold 7 very small fish (guppies, etc.), but not necessarily the fish you want.