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My research has led me to a number of husbandry blogs detailing water parameters, feeding schedules, lighting periods, and temperature manipulation. However, there is little information in the way of preferred cave size, shape, or placement. I am a chronic tweaker and plan to make my own terra cotta designs.

I can try different options to see what works best but would love to have a steeper learning curve by mining the collective wisdom on this forum. I know that this list of questions is exhaustive, but don’t feel you have to answer everything. Any information is appreciated.

For those of you who have successfully bred Hypancistrus:

Is there a particular shape of opening that seems more desirable: square, circular, rectangular, semi-circle, or triangular?

Do they prefer a tunnel of uniform dimensions along its length or one that tapers towards the rear?

Can you stack the tunnels into a condo arrangement to reduce the footprint of the aquarium furniture, or do they need them spaced throughout the tank for larger territories?

If the plecos do not mind a condo arrangement, is it still inadvisable to arrange them in a manner that requires you to disturb the others in accessing one?

Has anyone experimented with placing the caves at varying heights within the aquarium or is it a given that they should be placed near the substrate?

Where do y’all fall on the debate over the importance of a current across the opening of the tunnels?

Should I add a lip to the bottom edge of the tunnels to reduce the possibility that eggs will be “kicked out”?

Do you find it advantageous to have a removable segment to provide access to the interior or is that an unnecessary feature?

What are the dimensions of your favorite Hypancistrus cave, and which L number do you use it with?

If my plecos do spawn in the peaceful community, is it better to leave the fry undisturbed or to transfer the cave to a bare-bottom grow out tank?

If it is advisable to transfer, then do you just move the fry over or their parents too?

I hope that I have covered everything, but would be deeply appreciative of any information you guys might feel that I have overlooked. Thanks in advance for any help.

I'll answer what I know. I use caves that I have purchased from plecocaves.com, and are either cylindrical or square with the end squeezed off. Hypancistrus have bred in my 1.5" square caves. The males tend not to dwell in the round ones. I'd suspect triangular ones may also be liked, but as I said I only have square and round ones. I also have 1" caves, which are fairly popular for juveniles, and 2" ones, which are super unpopular.

Most of my caves rest on the bottom of the tank. I have never found a male with fry in any of the caves I have placed on other caves.

I've never placed a cave not on the bottom, but I'm guessing this would be pretty unnatural for Hypancistrus so I don't see any reason to try it.

Current across the opening may be important, but some of the species I've bred did so without any attempt to place current across the opening because I was still trying to just fatten them up. Off the top of my head, this includes my most recent breeding of H. zebra, but also includes some of my other Hypancistrus species.

All of my Hypancistrus appear to prefer the square 1.5" caves from plecocaves.com. There is some length to it which is something like 4-5", but this really doesn't matter since males advertise to females by sitting halfway out the cave.

As far as a lip goes, I have seen a few yolk sac larvae kicked out of a cave once or twice, but generally nothing leaves the nest. This is not much of a concern but it's not impossible.

Easy access into the inside of the cave to get juveniles out easily is awesome. Hypancistrus easily cram themselves into caves and it can be pretty time consuming to try to get them back out in my experience. Although I have a couple techniques to try to get stubborn fish out, some Hypancistrus simply cannot be extracted from caves if they don't want to budge.

I let the male take care of eggs and juveniles until he releases them, however my tanks are specific for Hypancistrus. If you suspect that fish may eat the juveniles, moving the entire cave (with the male to take care of the eggs and juveniles) might be wise, although I haven't done this before. Having the male take care of the juveniles is the easiest way to go about it. After juveniles leave the nest, or when it's obvious the juveniles have absorbed their yolk sac and are ready to go, I go through the tank and catch most/all of them and place them in breeding traps. Cleaning breeding traps regularly is important to prevent the fry from dying, but it concentrates the food and allows for quick and easy observation.