Who Gives A Fish Forums

Hi there,

I came across some info on neptunes and had a chat with a guy who's been into fish breeding for three decades. He swears neptunes can thrive in marine aquariums - we're talking full-on saltwater, not just a pinch of salt. Apparently, not many people are aware of this. What's your take on it?

It's possible with neptunes, but you gotta do it slow. I've heard black mollies can also be acclimated to saltwater, it's pretty interesting.

Neptunes in a marine tank would be handy for feeding to your frog or lion fish.

Handy for feeding to your frog/lion fish...

Probably not the best idea in the long run, though. Brackish and freshwater fish have distinct physiological differences, and repeatedly feeding them freshwater feeders can allegedly cause fatty deposits to form around the liver. Still, it's worth noting that neptunes can apparently tolerate saltwater environments with salinity levels of 150-200% if acclimated properly.

That's really interesting, I'd heard of Black Mollies being adaptable but not Neptunes. The thing is, would you even want to try it? It's one thing to know it's possible, but another to actually attempt it.

Would their offspring be born with that saltwater tolerance or would they need to be acclimatised separately?

I just thought I'd share this info, didn't mean to stir anything up. I was surprised to learn about this too, and I figured others might be interested. I also didn't know about the lionfish thing, that they shouldn't eat freshwater fish. It just seems like a lot of hassle and expense to buy marine fish for feeding purposes, you know?

Neptunes and mollies can be used as feed for saltwater predators, but not as a long-term solution. Acclimating neptunes to full salt takes a lot of time, we're talking weeks, whereas mollies can pretty much handle it right away.

Guppies on the other hand, seem to have trouble with full salt, especially if they're heavily inbred. Apparently, cross-breeding them with a wild form can resolve this issue. Time is key when it comes to acclimating neptunes, that's for sure. I've never actually tried it myself.

I'm even more impressed by neptunes' hardiness now. My god, they're tough.

Kryptic wrote: ↑Sat Apr 19, 2025 10:14 am Neptunes in a marine tank would be handy for feeding to your frog or lion fish.

Besides the issue of fatty deposits around the liver, the lack of omega-3 in freshwater organisms likely plays a role as well. There are probably other deficiencies and non-essential nutrients that come into play too.