Stocking ideas for this aquarium?

[Lucidahandwriting]

would be so so much easier to give you stocking suggestions if it was heated soft water. you rarely see small cold water hard water set ups with tannins. in general there arent many cold water fish. and theres very few small cold water fish. and most don't have much colour. whereas I could go on forever with stocking suggestions for a small tropical soft water tank.

that's why i'm looking for ideas haha, it's hard mode
We will consider a heater though

OP states it goes down t o 18°C/64F°. Endlers are very much Tropical temperature fish.

I know a couple of endler breeders that keep them without heater, in nature they live in very warm water but i think they can adapt well to different parameters, they have been found in cold or acidic environments in nature... obviously you can't keep them at 18°C forever, but some seasonal changes in temperature are reportedly good for fish health

Another option would be just picking up fish from local irrigation canals (that dry out in winter) and keep them for a bit before releasing them in the summer

EDIT: i may have remembered incorrectly about endlers being found as invasive species in temperate or softwater, that applies only to guppies as far as info on the internet goes

 

[WhistlingBadger]

Keeping wild fish can be very fun and rewarding. A couple of caveats to that: First, be aware that most wild fish from temperate zones, at least in my part of the world, tend to be aggressive and need MUCH more space than we can give them. Also, check with your local fish and game agency before keeping wild fish--it is against the law in many places, and you might need a special permit. Finally, keeping fish in an aquarium and then releasing them is a generally bad idea, and also illegal in many places. I'm sure you'll do the research. I just want to call some potential difficulties to your attention. I've learned these things the hard way.

 

[Naughts]

they have been found in cold or acidic environments in nature...

Can you provide links to this please? I only have information of their natural habitat being in Venezuela.

 

[Lucidahandwriting]

Can you provide links to this please? I only have information of their natural habitat being in Venezuela

Sorry, i may have made a mistake... i was sure i read about endlers being invasive in some localities with either soft or temperate water, but i can find mostly info on P. reticulata doing that on the internet
I'm pretty confident that considering their similarities with guppies they would be able to live and reproduce in various conditions, in fact there are various reports of endlers being kept in unheated or softwater aquarium without much problems

But yeah i'll edit the original comment

 

[Lucidahandwriting]

Keeping wild fish can be very fun and rewarding. A couple of caveats to that: First, be aware that most wild fish from temperate zones, at least in my part of the world, tend to be aggressive and need MUCH more space than we can give them. Also, check with your local fish and game agency before keeping wild fish--it is against the law in many places, and you might need a special permit. Finally, keeping fish in an aquarium and then releasing them is a generally bad idea, and also illegal in many places. I'm sure you'll do the research. I just want to call some potential difficulties to your attention. I've learned these things the hard way.

All the fish in my locality are invasive haha...... hahaha............
If i went for the wild fish route, i'd just use plants harvested locally or in-vitro cultures so that i wouldn't introduce new pathogens from aquarium trade plants (which is really the reason why you can't release wild fish)
The rest of the stuff there is taken locally too, the sand was extracted from a well and the wood taken from a construction site
The only problem would be maybe food? I'll figure stuff out about frozen/live food and make some conclusions

For the species, i already tried some of them out years ago in a 200L and the species i'd go for are either Rhodeus amarus, Gambusia holbrooki, small Rutilus rutilus or Misgurnus anguillicaudatus