WOW...... This is going to be a great pond. Please keep the pictures coming!

Very nice. Really like the rock shoals, DW has a very good eye. Using big rocks is smart. Once algae covers the rocks a bit they tend to disappear a bit, bigger rocks disappear less.

Some things you might want to consider...

It looks like there are some gaps in between rocks that could be filled with a little bit of mortar. I know the look you're going, you want natural not mortared rock wall, so you don't want to grout them all. But when they're underwater things change. Just like in natural gaps will fill with muck. And you won't be able to see these gaps as well even with no algae. Not a big deal but imo, better to fill with mortar. You can still leave deep gaps, but they can be filled a bit. At least as far as I can tell from the pictures. Not saying this is important at all.

The cracking mortar isn't a big deal of course. For other readers... Reducing water in mortar reduces shrinkage. Like dry mashed potatoes. Two 1/2" coats would reduce shrinkage. Or doing small sections. Each section shrinks and then an adjacent section is done. The shrinkage crack would happen where it's thinnest, over the folds.

You can fill the larger cracks, like say more than 1/16", if you liked. This is a good idea to lock it all down, but not super important.

What is kind of important is to wait 3 or 4 weeks before filling with water. 4 weeks is best. You can wet it down right away, a little standing water would be OK. There is a lot of debate on whether keeping cement damp is needed. 30 years ago it was a requirement. Cement never stops curing and it does need some moisture. So to me, in summer, I do think it helps. And it's so easy being at the bottom of a pond.

The 3 or 4 weeks are needed for the crystal structure to form enough to be fairly waterproof and to completely enclose the lime. If you add water too soon the lime can leach out and weaken the mortar a lot. People fear the lime leaching out and causing high pH and can be a small issue with uncured cement. But the weakening of the mortar is of more concern imo.

Before filling the pond hose down everything. Mortar, rocks, liner, until there's a few inches of standing water. No reason to scrub anything or use anything other than water. Let that sit for 12 hours or longer. Pump out that water. Now you'd be ready to fill the pond. This wash down gets rid of dirt and mortar dust and gives any surface lime a chance to dissolve into the water.

Some people might tell you to wash the mortar with acid to "remove the lime". An acid wash has the opposite effect. The surface of cement reacts with CO2 forming a kind of "rust" called calcite. The CO2 can be in the air or water. Calcite has a pH of about 7 and helps seal the cement beneath. An acid wash would dissolve the calcite leaving fresh brand new cement with a surface pH of 12.

Formation of calcite is also why you don't want a lot of standing water during the cure. You want CO2 in the air getting to the cement.

WOW! Thanks for all the helpful info waterbug_guy! This pond is really shaping up!!! Love the rockwork! The waterfall is gonna be amazing I'm sure!!!! So glad you found the forum and post these work in progress pics!

Thanks Holly & Calamity_j. I'll keep updating every weekend we get to work on it (which will be pretty much every one...)

Aw shucks, Waterbug! Okay, we'll wait to fill it with water, but I really wanted to see what it looks like. ;) The delay is to allow the mortar to reach full strength? I was planning to make the basin for the waterfall also out of mortar. Would you advise a similar wait period for that, even though we are talking about 6" of water?

Took your advice and hosed it down this morning to keep it damp. Rocks looked much better wet, but much of the water percolated down the cracks. I am a tad concerned that this means that the mortar is not at all adhered to the liner?

Since we can't fill it this weekend, we begin work on the waterfall. More rock hauling! Yay!

Cement never reaches full strength, it never stops curing. It's weird stuff. So a premix supplier will say a product strength is 400 psi in 24 hours, 1000 psi in 7 days and 3000 psi in 28 days. So on the bag they'll sell it as 3000 psi. But after 12 months it might be 3100 psi. So 28 days is just kind of a standard.

But I'm going to research this some to see if I can give you a better answer. Not a lot of data for curing mortar underwater. BTW, what brand mortar mix or Portland cement did you use? The kind of lime is important for how it cures.

OK, I checked Portland Cement Association and Quick Crete web sites. Mortar isn't really rated by strength, so the 28 day thing really doesn't apply. Both said portland cement (I assume that was what was used) will cure underwater. They both said that most of the curing happened in the first 7 days. That's also the period they said to keep it moist. Temp is a factor but you're OK there.

So I'd say 7 days would be enough. And actually, if you wanted you could anytime. I'd be interested in the result that is for sure. I never filled a mortared pond in less than 4 weeks. I don't think there would be a big down side.

If you filled it right away I'd be interested in pH levels you see. I think it would be smart to add pH buffer (baking soda, measured by KH) right away and have good GH level. That's good to do whenever you have fish and you don't want any acid produced using your fresh mortar as the buffer material. I think pH would have to get down into the 5-6 range, but no sense taking the chance. 5-6 pH would weaken the mortar.

Mortar doesn't adhere to liner, at least so weakly I'd say it doesn't. When it hardens around folds it can get locked in pretty well though. But that's no problem for the bottom. If you go up the sides it is an issue and I talked about that I think in a previous post.

Thanks for posting your update photos Mike and DW. It just boggles my mind that you 'found' that in your yard. It is going to be really cool, can't wait to see.

Your rock shoals reminds me of a youtube video I saw awhile back about a 'koi tunnel' in a pond. In this video, the koi tunnel was a large (8" or more) section of PVC pipe that was laid vertically on the bottom of the pond then had rock placed over it. I think I remember you saying something about fish. Fish like to have someplace to just hang out with something over their fins. Helps to protect them from hungry birds of prey. And hungry reptiles.

Last fall I watched our neighborhood Coopers Hawk perched over my pond waiting for sushi snacks. That (and the leak) was the final push to rebuild my little pond. Second time around, I built in many various size 'tunnels'. Floating islands work well also.

~dianne

Waterbug, really appreciate the feedback on the mortar. We are using Quickcrete type S mortar. I looked it up before buying it, and it was supposed to be strong but have some give. I also saw the curing strengths over time, but figure if you have experience that's more convincing than the manufacturers promises, I'll go with that. : ) Now, I have kinda spooled up to rock the waterfall, so maybe we'll split the difference and fill after two weeks.

Dianne, you should have seen it when we found it.. 3/4 filled with leaves from the acacias and covered in English Ivy, the second most evil plant in the world (behind kudzu). As far as fish tunnels go, there's the little channel that connects the "big pond" to the "little pond", and we were thinking to place some big rocks over that to make a sort of fish tunnel. We also have hawks, as well as raccoons, owls, herons, possums, blue jays... We will also add some other areas where the fish can take cover. We are planning to add an arched bridge over the big pond, and have a small rock island. They should both help make the fishies more comfortable, I hope.

Did you post any pics of your pond rebuild? I'd like to see. : )

I always try to follow manufacturer instructions. But they don't provide info specifically for every use, like underwater.