My friend keeps zebra danios in unheated weird community tank and they are fine

[Markfishguy]

My friend has a tank with virtually anything he can get.

It includes tropical fish and even crawdads from the local river.

I can't believe everything is healthy and in unison after many years. Goes against every principle of keeping a tank healthy and I've had Danios die for absolutely no reason trying my best to create the most healthy tank ever lol

 

[JuiceBox52]

Zebra danios are a cool water fish, so don’t require heating

 

[GaryE]

If you look at a non aquarium site like fishbase, you get the natural water conditions for species. Danio rerio, the zebra, runs from 18-24c, and thrives in unheated tanks if your house is reasonably warm in winter. Kept too warm, they live shortened lives.

What they need is moving water. Those are racing stripes on their sides. They love to swim in filter outflows, and stream tanks make them happy.

 

[Slaphppy7]

Welcome to TFF

There's a big difference between surviving and thriving

 

[WhistlingBadger]

I'd be interested to know what other species he keeps. Many "tropical" species thrive in cool water, and crawdads can live just about anywhere as long as the water's fairly clean and not too warm. Sounds like he chose a random assortment and got lucky.

 

[Byron]

I can't believe everything is healthy and in unison after many years.

You and we cannot possibly know this to be the case. Environment significantly affects a fish, all fish, and if it is outside the parameters for "x" species it will have an impact on the well-being. We cannot always see this, until it is too late usually, but it is there. Weakening the fish, allowing it to become more affected by this and that. "Environment" here means all aspects of what the fish needs in terms of water parameters, habitat/aquascape items, numbers, other fish/critters, etc.

The problem with your danios has a cause, something you did or something you didn't do, respecting the water, tank size, numbers, etc, etc.

The only way we know fish should be healthy is by providing what the species expects and needs, and this has come from the evolution of each species individually. It is literally in their genes.

 

[emeraldking]

My friend has a tank with virtually anything he can get.

It includes tropical fish and even crawdads from the local river.

I can't believe everything is healthy and in unison after many years. Goes against every principle of keeping a tank healthy and I've had Danios die for absolutely no reason trying my best to create the most healthy tank ever lol

My zebra danios are swimming outdoors in a tub of almost still water. But the breeze makes some movement on the surface. They can be kept unheated. And I don't do any water changes. It's the rain that will fill the tub with water. But there's substrate on the bottom and pond plants. And those fish are completely healthy and do reproduce in there without any problems.

 

[Ichthys]

When I was in the trade one of the shops we supplied kept his zebras in an unheated tank in a shed, moving them into the shop as required. Temperatures down to 5-6C in winter. He did it because they survived well, and had heightened colours when he moved them into the shop. I saw them a few times and they were very active, just like they are when they’re warm.

 

[Colin_T]

We kept them in unheated tanks in the shop.

Danios need a cool period so they don't age as quickly and so they don't become egg bound. This happens a lot in tropical tanks whereby the females develop eggs and get fat, but the males won't breed because they need cool for a few months then warmth to come into breeding condition. After a while in warm water, the eggs solidify and the females can't breed.

 

[GaryE]

"Temperature creep" is a feature in our hobby - over the years I've kept fish, I see suggested temps getting higher and higher. Don't take advice from fellow hobbyists. Take 5 minutes and look at local conditions where your fish come from.

Too warm or too cold has a larger effect on cold blooded animals than it does on warm blooded us. There are species whose digestive enzymes are temperature dependent, and who can't grow properly out of narrow ranges.

Most aquarists don't breed their fish, so they don't see the problems someone keeping their fish through a few life cycles might. But the wrong temperatures can affect immune systems, and so many other issues.

Danios need a cool period so they don't age as quickly and so they don't become egg bound. This happens a lot in tropical tanks whereby the females develop eggs and get fat, but the males won't breed because they need cool for a few months then warmth to come into breeding condition. After a while in warm water, the eggs solidify and the females can't breed.

I wish I had seen something like Colin's posting when I was a kid trying to keep zebra danios too warm and constantly losing fish to egg binding. I had perfect conditions at hand just by following the indoor temperature cycles with the seasons, and I stuck heaters in those tanks...

 

[emeraldking]

Take 5 minutes and look at local conditions where your fish come from.

Well put...!

I see suggested temps getting higher and higher.

If you've read my replies on topics, this is something I often mention that the advised temperatures are increasing in an exaggerated way. But again, a lot of people think that all those fish kept in fishtanks are tropical.