Is it possible to get Ancistrus to breed in a rock pile or do you need those eye sore pipe caves everyone is using. I really don't want to taint my fish tank with one of those.
Okay, so first off spL144s aren't the easiest of the Ancistrus to breed BUT you will NOT want to add any other kinds into the mix, to ensure proper breeding. Hopefully both your males and females all came from the same place, to ensure this.
To answer your question YOU CAN BREED THEM WITHOUT TUBES. But will need to build "caves" somehow, as they only breed in caves. It is genetically Incorporated into their instinct to protect themselves, their eggs, and their spawn, by breeding in caves. I will go thru a short list of things you will want to use as caves, instead of the ugly breeding tubes, that you will want to have a combination of. The second portion of my answer elaborates on the best conditions you can try to make possible in your tank, to increase your chances of breeding.
For caves, you will want slate or large flat rocks to build your own cave. Stack them, and lean them against each other in a manner that allows an opening for them to get in and out of and the inside should be snug enough that little light reaches inside. Pic below, dark blue-ish grey slate, peices together and glued with aquarium glue (common product in fish stores that sell reef tank products). Strive for almost complete darkness. Using aquarium glue (waterproof and fish safe) may help to create that darkness- see pics. You can either make the opening on the bottom, side of the cave OR a small hole at the top (although this option let's more light in, depending on your rocks or slate this might be the easiest, although less ideal). If you choose to have the "door" or opening on the side, make sure you have two caves like this, one facing the back of the tank and one facing forward, so they have more options. They may feel safer going to the back door, than the front, where there's more activity aka more threats. See pic of terracotta pots with front and back opening. Put driftwood in your tank. Also lean peices up against one another in a manner that creates a dark space for them. Normal off the shelf decor- if you can find a terracotta cave in your pet store these are good options too. Some decorations are even painted black on the inside, which will help to keep lights out as well. Pics below of a few decorative cave options pre built.
General condition recommendations: "Breeder tanks" aka long tanks are best for producing young. 10gallons are difficult, the easiest are 20 or 30 gallon tanks. You can do larger but you want lots of interaction between males and females, so the larger the tank, the more of them you'd want in their- best to stick with 20-30 gals, but bigger isn't impossible. 10 gallon is just harder to offer multiple caves. These fish have a very high protection trait when breeding, which also means you'll get best results if you breed in a separate tank than with other fish. You will want at least two or three females per male. An ideal breeding situation would be two males per five females. You will want a spong filter OR need to wrap netting around the intake of your filter to keep eggs and young from being sucked up (I breed fish and use the net option, because it's cheaper that buying an additional filter), but if you need to get a new filter for your set up anyways, try a sponge filter! Your tank needs high light (during daytime only) and a heater at all times, kept between 77-80°F. Use little or no substrate on the bottom. I prefer a thin layer of substrate, either sand or small sized gravel bc the reflection of the light bouncing off the bottom glass can spook fish AND because it's cleaner and prettier. BUT if you choose no gravel (so babies and eggs don't get lost or crushed in substrate) put black or natural colored paper, cardboard or aquarium backing under the tank. Feed high quality algae disks; look for one that includes spirulina, and even better if it also says it has veggies in it. Supplement with real veggies; rinse, cut into 1/2"-1" sized peices, and blanche zucchini and cucumbers. Blanching them keeps them from floating. Check and keep up with tank quality. They can thrive and breed fine in hard or soft water, and a pretty wide pH (6.4-7.8), but you want your pH and hardness to STAY consistent to reduce stress and change. Keep the water CLEAN, 10-20% water changes 1-2x/week until eggs are laid, never moving caves. If you do a 20-25% water change 1/week, you'll be less likely to disturb their routine, but s keep the tank clean enough. You are not likely to produce eggs and spawn if your ammonia spikes, and is just unhealthy anyways wether breeding or not. Always turn lights off at night, and try to have regular feeding schedules too. When you start feeding veggies (especially important to give after eggs hatch) remove after 8ish hours. People say 4, but not all fish have discovered the veggies in time to get much snacking out of them. I'll drop veggies in before I go to bed, and take them out in the morning, which may work for you too!
The original question specifically described clay breeding pipes as "eye sore pipe caves," implying the asker prefers a natural look. Use driftwood!
All a male ancistrus needs is a concave or hollow piece of driftwood, or even a flat piece of driftwood stacked or slanted to form a hollow. I prefer concave pieces, allowing the large male fish to dig holes in the gravel without collapsing the cavity. Most ancistrus benefit from having driftwood to chew or scrape, so providing a natural wood cave delivers two benefits.
You can often find a small piece of hollow or concave driftwood between 6-8 inches long (15-20cm) for low cost in a fish store, because the pieces are sold by weight and you only need a small piece. You can even hide it in a corner, but it is more fun to point the opening toward the glass so you can see the eggs inside. Be cautious of using wild wood, as you don't know what toxins it may have absorbed.