I don't think that's taking it slowly with adding fish. Your tank is nowhere near cycled and those plecos will have a big bioload, which with that small volume of water, you will see the ammonia rise rapidly and the tetras will suffer unless you are monitoring it very well. Water changes are also going to be rough as ypu cant take more than a few gallons out at a time.

Either way, not the stocking choice I would have made but it's your tank. What kind of plecos are they?

That does suck about the eacapee. Hard lesson to learn.

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