I've three ottos in a planted twenty high with 7 long fin zebra danios and 2 female platys. The plants are well established, almost overgrown but I like it this way and everyone's seems happy. When it was a little less lush I could usually find an oto or two or even three. Now I've only seen one in weeks. I'm looking for little oto corpses and not finding any even when I vacuum. Is this normal? Are they that good at hiding?

In a heavily planted tank...they are very good at it.

Very normal. My oto's live in a big tank busting amazon sword and are rarely seen.

they're pretty much invisible. you probably won't spot one very often if at all.

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It's abnormal to be normal.

I'm sorry, my Karma just ran over your Dogma.

They're still there but pretty much invisible. The tank is now heavily planted thanks to nature's abhorrence of vacuums. I'm thinking of switching to all otos and letting them breed. Any problem with mixing varieties?