Why have my BN stopped spawning? bring me the experts.

I get my caves from Rosenthal Pottery, here's a link. http://www.rosenthalpottery.com/plecocaves.html I use the #4 caves. started out with the ones that taper to a point in the back and switched when I had a female get her head stuck in the back of it behind some eggs. I only left my first spawn on it's own in the 75G. It's very thickly planted. I thought it would be ideal to for the pleco fry to start off. I had seen the spawn before they left the cave so I knew about how many there were. As I watched the tank, they seemed to not grow as quickly as they should. You can't feed the fry constantly in a large tank like that, they need to eat constantly. So I pulled them out. I found at least half the fry had disappeared. I figured it was from lack of food. I don't think the embers will bother them once they loose their egg sacks and stop floating around. If they were regular bristlenose maybe I wouldn't care that half of them disappeared, but the L144's are too valuable to loose so many and the spawn sizes are much smaller than the pucallpa bristlenose I was raised. The pucallpa's would have at least 100 at a spawn.

I think they will definitely choose a small protected cave over another place in the tank. You should see the males go in the cave frequently about a week before the female is ready to mate with him. He cleans and cleans it. Tidy little dads!
 
Here are some pics of the fish. At least we can be sure they are well fed and have plenty of driftwood to rasp on.

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They are beautiful! That brown female's getting nice and plump with eggs!
 
I'd raise the pH to 6.5 or higher, if they were mine. Do a couple big cool water changes and you should see a spawn in a week or two. IME, common ancistrus don't see the humor in a pH below 6. If you want to spawn fish in those parameters, you should look into a blackwater species like L180 or L183. Putting an air stone in the tank to offgas CO2 at night might also push your dissolved oxygen levels up and that can make them more amenable to getting frisky.

Barbie
 
Thanks Barbie. The CO2 is on a PH controller, it turns off automatically so it stays constant and the gas doesn't run at night. I have decided to turn off the CO2 completely for now just to see if that was having an effect, and suppliment with half doses of excel instead (which won't effect pH at all). I am reluctant to add anything to increase pH becasue I always do more damage than good when I mess with it chemically. If the pH doesn't come up to the mid sixes without the CO2, I will add a handful of crushed coral to the filter and see if I can up it that way.

I baked some sculpey clay caves (4 of them) today, and added them to the tank. Each is a little different, taller, or squatter, or larger or smaller, so the 2 males can pick the shape they like best. Each has one opening roughly 1" wide by 1/2" tall facing a pane of glass so that if I have to I can shine a flashlight in through the glass and see who's home. I have hid them in the java ferns. It is amazing what you can hide in all that mess. I've already seen tails swishing around inside some. No one has had a chance to "move in" yet but they are definitely "house hunting"
 
Swishing tails and house hunting......good signs!!!! LOL! Keep up posted!
 
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