How many guppies it too many for 75 gallon?

  • We are currently upgrading MFK. thanks! -neo
Bump it up to an 80% once a week, heavily plant it including floating plants and java moss, increase the filtration, and as long as there aren’t more fish than water you’ll be good. At least that’s what I would do. If you’re insistent on the 2 25% weekly water changes I’d just wait and see what the parameters say as the guppy population increases.
 
Let the tank tell you...

As this is not a show tank, but just a breeding tank, I'd put a bunch of pathos or other easy to grow, hardy plants in it, stock it and let it go. Watch the parameters and service it as needed. I don't think you'll need much filtration. No more, probably less, than a typical 75 Gal cichlid tank. If you plant it well enough, I don't think you'll need to do many water changes either. As someone who is prepared to do 2 water changes a week, just keep an eye on it and do them as needed.

I have a 150 Gal Rubbermaid stock tank filled to an estimated 120 gallons of water. It houses a large breeding colony of Endlers (I'd estimate 1,000), a few pairs of Apistos & fry, a few L333 Plecos and a few Mexican Orange Crayfish. It's very heavily planted and has a single powerhead for "filtration". The bottom of the tank gets broken down plant matter that would be an eyesore in a glass aquarium due to the lack of mechanical filtration. But it can run indefinitely and never see any ammonia/nitrite/nitrate. The plants eat every bit the fish add. That said, I still do water changes of 20-40% every other week or so. But if life got busy I wouldn't hesitate to skip them on this tank for months at a time.

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