YoYo Loaches and PVC Pipe

[DFly]

I am think of putting a cave network under the sand of my new 29 gallon using some PVC for my YoYo Loaches. Would 1.5" PVC be large enough? I have not been able to find sizing information on their diameter.
Each cave is going to be a 3" piece of with cap then a reducer to a Z connector with an 3 " above ground 1.5" pipe. I made the top of the cave see through by cutting a hole in the 3" piece of piping and gluing a sheet of tinted acrylic over the hole so I can spy on them in their "dens". Essentially make a buried under ground cave. Would a 1.5" pipe allow one directional movement (entering and exiting)? Would a 3" piece of pipe work to allow them to turn around? Originally started building these with Kuhlis in mind but now have yoyo loaches planned. There is gonna be 3 of them, 1 for each.

 

[DFly]

Posting a diagram because I know my description is horrible. https://imgur.com/a/QxcSA

 

[DFly]

Duplicate Comment

 

[Autumnsky]

I am thinking you might experience issues with stagnant water. Maybe holes drilled for flow?

Why so long and z shaped? Maybe unnecessary?

I really like the spy/viewing window.

How will you keep them anchored to not float?

 

[DFly]

I can easily put some holes in the top of the den and in the tubing, that is a good idea.
I made it so there was no sharp angles because I was afraid the sharp bends would impede a fish from getting in and out. It is probably unnecessary with such flexible fish but I was worried a loach would get in there and not be able to get out. I got the idea from seeing some PVC turned into above the substrate caves, so I wanted to try some subterranian caves. The whole unit is only about 9-12" which isn't horrible long for my 29g.
The keeping them sunk part I am still workin on. Once they flood and are buried in sand they are fairly stable especially because I glued sand to the surface of the pipes to disguise them and filled them with a bedding of sand. My plan is if they don't stay stuck is to glue larger rocks to the base to add additional weight.

 

[Autumnsky]

Okay, a siliconed chunk of slate would work if it doesn't stay put.