I'm worried my brothers turtle tank doesn't have enough bacteria since he didn't cycle it before putting in the turtles. He has 3 baby turtles and a goldfish to clean up uneaten food in a 10 gallon tank with a 10 gallon filter.(Yeah, I know he needs a much bigger filter) Can I transfer bacteria from my fish tank to his turtle tank? If so, how could I do that? I don't think I can put few of gravel in there because the turtle might eat them. Also can I feed the turtles tadpoles?

What kind of turtles are these? I would imagine that they barely fit in a 10g tank, and if they do they probably won't for very long, so at least think about upgrading to something larger than a 10g tank. Even if they are spotted turtles, which stay small, that tank is too small. You should be able to feed the turtles tadpoles; they usually like earthworms too. Peas are good veggies to try to feed them as well.

Yes, you can transfer bacteria from your tank to his. You can take out some filter media from your filter and put it into the other one. At least that's the easiest way to go. You can also add a product called "Cycle" which helps to boost the load of beneficial bacteria in the system.

Tell us more about his setup and what's in it please so we can make some recommendations. There needs to be a better/bigger filter for sure considering the bioload of the tank, unless he's planning on changing the water every other day.

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When in doubt, do a water change.

Turtles can come up for air and if his tank is setup so that they can get out of the water, they should be ok, but your goldfish will suffer. Not only is it in the water the whole time, it is a poop factory compared to other fish and will definately spike the tank with ammonia and nitrates.

If you have similar filters just transfer your filter media to his, or add some of your gravel, plants, or any decorations to his tank. If your filter will work on his tank, you can also "swap" filters (but rinse his out) since your tank is cycled and the majority of the beneficial bacteria is still in your gravel.

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--->Pictures of my 75g Amazon tank<----

His filters smell horrible. And it's obviously overloaded. I'll need to buy a second filter. I don't remember what type of turtles he has, we plan to move the turtles into a much larger tank this summer when they've grown. I'll also get him to feed his turtles in a separate container to reduce the load on the filter.

Definitely overloaded. But I'm glad to hear he'll be feeding them out of the water; that should help minimize the waste. Though I doubt the goldfish will do well...

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When in doubt, do a water change.

I'll just change the water more often.