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FAQs on Water Feature Rock Use/Making/Repair

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Rockwork needs to be inside the liner or outside, not through the basin edge

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
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Volume 2. Maintenance, Stocking, Examples

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by Robert (Bob) Fenner

Fishpond, rock/coloring   10/12/09
I have built a concrete lined fishpond and have sealed the concrete to make it waterproof by fibreglassing the surface. It holds water beautifully without leaks but does not look very natural as the fibreglass resin was
grey in colour. I want to make it look like natural rock (sandstone) and have thought of the following method:
Paint the surface with waterproof paint and then before the paint dries sprinkle it with cement colouring oxides of the right shades.
<Can be done>
My question is will the oxides be toxic to fish?
<None are toxic that I'm aware of. Our company used such to dye mortars in making artificial rockwork for years>
Please respond as soon as possible.
Kind regards
Selwyn Adelson
<Bob Fenner>
Re: Fishpond, coloring oxides  10/14/09

Dear Bob,
Thanks for your prompt response - it was much appreciated.
Kind regards
Selwyn Adelson
<Welcome Selwyn. I have used literally thousands of pounds of these coloring oxides in making artificial rock and coloring cementaceous materials in ponds, biological and not. Cheers, BobF>
Re: Fishpond  10/14/09

Dear Bob,
I have now used the oxides sprinkled onto wet pond paint and before the paint dried it started raining. I cursed my luck but in fact it worked out very well as the rainwater blended the colours into each other and now that it has dried it looks stunning - just like natural rock with a subtle gradation of colour.
Thanks for your help.
All the best
<Thank you my friend. BobF>

Pond Rocks 5/17/08 Would it be ok to use limestone rocks for a pond? I will have goldfish and plants. Thanks, Renee <Such calcium/carbonate rock can be employed IF it does not change/alter your water quality too much... goldfish can tolerate quite hard, alkaline water... as can many plants (not all)... I would be investigating the needs of those you have in mind, testing the water for pH, alkalinity. Bob Fenner>

Faux rock repair around my pool  9/2/07 I live in Las Vegas. The faux rock waterfall that is part of my swimming pool has started to crack in various places. The calcium from the salt system leaches into the cracks. The pool is 7 years old .The rocks are a typical wire mesh/rebar/stamped & stained concrete variety. The cracks themselves are no bigger than 3/32" wide, but some are as long as a foot or two. Researching the net doesn't really address a specific technique....could you be so kind as to advise me on a DIY??? respectfully, Michael Best <Mmm, yes... there is a Thoro Product called Water Plug that is a very fast-setting mortar that actually expands when it cures (most cementaceous materials shrink)... I would get this, and an oxide to color it (take a sample of your rock to a stucco company and they'll match it for you), mix the two together dry... in small batches (the amount you can use in under five minutes). Apply with a sharp trowel, wipe with a yellow sponge that is damp... Voila! Bob Fenner>

Water sealant for Koi pond waterfall   8/24/07 I have a Koi pond (see www.interall.co.il/pond.html <Nice pix and great documentation of your project! Glad I wasn't there digging when you hit those rocks!> for further details) and I would like to use a water sealant on the edging stones as well as the waterfall stones so as to inhibit Ph rise (Ph is at 8.4) as well as GH (16) and KH (10) rise. I have found Thompson's (r) Water Seal (r) Clear Multi-Surface Waterproofer http://www.thompsonswaterseal.com/products/list.asp?show=home.products.wtrPrf.multi and was wondering whether over time the sealant would leak into the pond. Thanks, Hank <Mmm... not much of an issue... as the material is quite chemically inert once it is cured... But... don't have much confidence that this application will last... or get you "where you want to go" here... How hard, alkaline is your source water? I might set up a trash can... near the pond... to adjust the water quality over time/changes... and use some live plant material as a mediating influence in the meanwhile... Not (too) hard to slowly drive, modify water chemistry over time here... Bob Fenner>
Re: Water sealant for Koi pond waterfall   8/26/07
Thanks. I can redo the application every year if necessary. I have various lilies, water hyssop, water hyacinths (which I control so as to not overload the pond) in the pond. -Hank <Ah, good... about half the surface area for plant cover should be fine. Bob Fenner>

Flagstone... use for? I recently purchased some flagstone from Home Dept. I have looked all over the internet and your website for specifics on safety of Flagstone. Is flagstone as safe as some of the other rocks? <Mmm, most such rock is composed of sandstone... in turn a mix of mostly silicates (largely chemically inert) and some other material with variable solubility... IF you're using this material in a setting where the water is not too acidic, or alternatively don't mind/can use the slight alkaline reserve this material will impart (e.g. Great Lakes African Cichlid, Central American biotopes, as a surround on a garden pond... there is not likely a cause for concern... I would NOT use this material in most marine aquarium applications... more for the need/use of more soluble calcareous material, than toxicity issues. Bob Fenner>

Lifting boulders out of pond to patch flexible liner  - 03/24/07 Hi there,   I am hoping you can help me figure out what I need to do to levitate a big boulder so that the flexible pond liner underneath can be repaired.  (The aftermath of a shady contractor.)   I have thought about using an engine hoist, but they are designed to be used on a level surface and would not straddle the distance needed to be on the stable banks about 6-8 feet wide.  I have thought about a installing a boat hoist outside the pond, as well.  I have also thought about (simply) rolling it out of the pond and banishing it to the status of land-based rock feature outside the paradisal pond.   What think ye? Thanks, Jody <Mmm, first and foremost to make cautionary remarks re smashed body parts... Remember thou art mortal! Secondly to state that any movement of this rock, smooth or not, may well tear your liner... So... Do get, place "carpet remnants" or samples about one edge/side... and with lots of coordinated, strong friends... with good backs... lift... with your legs... the rock onto the aforementioned carpet... and scoot more of the same under the edge just lifted... go over to the other side... lift and scoot the carpet pieces further in... Am hopeful this rock is not too large/heavy to allow this prep. work... IF there is sufficient stability, AND room around the edges of this water feature... you may be able to "chain" this rock (securely... with bolts, washers, nuts twixt overlaying links... Tie all this to some sturdy lumber of sufficient length to straddle the pond... re-locate those friends we listed before... and brute-strength, lift this rock out... more carpet pieces laid out in the direction the rock will cover is recommended... DO be careful... and please write back if this rock is too "round", heavy... there are other possibilities. Bob Fenner>
Re: lifting boulders out of pond to patch flexible liner
 - 03/25/07 Hi Kind Crew, Thanks for the prompt reply and the caveat about the squish-crunch factor (ah, the endoskeleton!) <And meso and exo...>   The good news is that there's plenty of room around this flat-ish boulder which is sitting on a @ 10-inch high 'pedestal' of stacked pieces of recycled concrete although it is about 4 inches below the level of the bank.  Would it be feasible to place beefy timbers at sufficient width on both sides of the boulder (with liner gathered up like skirts so timber guides rest on dirt) and slowly, carefully.... many chains, bolts, overlaying links strong backs and many tamales later... <Don't forget promise of cold brewskis later...> have the damn thing out of the pond never to return again? <Yes... Do bear in mind... a useful "rule of thumb" that the rock likely weighs about 200 pounds per cubic foot... and do "loosen" it from its perch... likely with a crow-bar or two... or metal pry bars, digging "sticks"... ahead of attempted lifting>   I could also gather the skirts pad with carpet, pack dirt around the boulder, in effect drawing the shoreline closer, and roll the thing over and over and away. Given the thus exposed loosey goosey liner (all rocks, plants, water removed,) I would plan to install many layers of liner to prevent further episodes. <One good one should do it... Tetra's 32 mil... or a nice, thick EPDM/Butyl...> The contractor used an old rubber-backed rug as cushion on the upper part of the pond, but none beneath this section of the pond which houses the mammoth rock, doh! <Indeed> Nothing like experiential learning, ahem! <Mmm, I'll cut the first-hand experience here m'self>   What are the other options?  This is about a 1-ton rock, <Oh.... really too big... heavy... see below> originally placed with a back hoe... <Can you get one of these back there? W/o too much damage?> The distance from one side of the pond to the other where there is stable ground is about 14 feet, larger than I would've eyeballed it to be.  So 14 feet is the distance any contraption would have to span in order to levitate the rock. <... Ohhhh>   So the challenge is to lift it about 6 inches, let's say, and potentially move it about 6 feet to the bank and possibly leave it out permanently. <Mmm, yes> It could look just as pretty at the edge of the pond.   When this rock is no longer there and there is in effect a swimming hole in the pond, do you think that having a layer of rocks, sand and gravel on the bottom would pose a great friction problem should a certain pond-wader find her way into the water when it is 112 thousand degrees outside in summer here in Pasadena, CA? -Jody <I would "cushion" the entire bottom where the liner will rest... Actually, having been involved in a couple hundred such installs... let me "cut to the proverbial chase" here and state that I would definitely NOT make this just a liner pond... but use the liner (as we used to) as the underlayment... Later on this... The rock I would actually "bury"... too big, much trouble to move... not likely easy to break up in place... I would dig a hole near it... and roll it over, in essence, bury the thing under the future pond... And make the pond as detailed here: http://www.wetwebmedia.com/PondSubWebIndex/Pond%20Sub%20Web.htm The second tray... Concrete and Liner Pond Construction... Read and heed. Bob Fenner> Re: lifting boulders out of pond to patch flexible liner  03/25/07 Hi Bob, Thanks for the link to the website.  Well, the rock, though 3 feet across, 4 feet wide, and about 18 inches high, must not be a ton b/c it's now sitting pretty on the bank of the pond.  (Two crow bars and three strong backs later.) <Very strong...>   I will purchase the underliner and cushion the liner with a double layer of the underliner fabric.  Is it necessary to have more cushion, such as sand, given that the dirt beneath is FREE of roots, gravel, and other disturbing bits? <Mmm, no... good insurance though... as is staying out of the pond yourself>   And.. I will simply not use the pond to wade in, and that's that. <Heeeee!> Thanks so much for being available and sharing your hard-earned pond wisdom with me! -Jody p.s. I will read again your section on container ponds b/c I have a couple of barrels with black plastic liners (like stock tanks) that I could aqua-fy to good effect. <Ah, good. BobF>

Reusing Dried Rock...Not Always Good - 09/29/06 Hello, <<Howdy>> I was doing some research on live rock and could not come across anything on this. <<Okay>> I currently bought a saltwater aquarium from a friend who decided to quit the hobby.  I bought the aquarium about 3 or 4 months after he had drained his aquarium, and he left his 30 lbs. of live rock outside in the sun for that amount of time. <<"Live" no more...>> So I took it deciding I might could use it later to maybe seed it with fresh live rock. <<Will never be "the same" again>> Ok so here goes, is the live rock officially dead? <<...as the proverbial doornail>> I assumed it was so I placed it in a garden pond with goldfish outside of my house to let it just sit, but red algae is now starting to grow on the rock. <<Yikes!  Depending on the size of the pond, this rock can raise the pH well beyond what is comfortable/healthy for the goldfish.  At the very least, the (likely) low pH of the pond will have sapped much of the buffering capacity from this rock>> I was just wondering why this is happening, because I'm not expecting anything to happen, and this is freshwater. <<This has nothing to do with whether the water is "salted" or not.  You've seen algae grow on rock in fresh water haven't you?  Same thing happening here...though this rock likely had dead/dried organic matter deep inside that once the rock re-hydrated, is now contributing to a Cyanobacteria bloom on the surface of the rock.  Nothing strange going on here>> I was just going to use it in the new tank after a while to see if it could be seeded from other live rock. <<Could be used as "base" rock (after a few soakings/rinsings), but will never regain the biota it once had and may have little if any buffering capacity left.  Personally, I wouldn't use this rock to build a captive reef...maybe break up/use for frag bases>> Any information would be great, just wondering why its growing red algae.  What's going on? <<As explained>> Thanks, Cody <<Regards, EricR>>

Faux garden rock enquiry  12/13/05 Hi Robert, I have just read your "Rock Selection & Use" at the wet web media site. I am a grandmother and want to make some easy to handle rocks to place in my garden. Are you able to help me with a recipe and the how to, to accomplish this?    <Mmm, I think so... are these to be of size, number? If not many and small, there may be a possibility of purchasing simple ready-made ones...> Any help would be appreciated. Doesn't seem to be much know-how around to help the crafty people.  Hope you can,   regards Yvonne <Consider making frames of wire mesh, covering these with canvas bags (like those used for commercial vegetable handling), and coating this with colored mortar... With a bit of practice, easy to shape final coats with trowel... Larger rock can be supported with tied re-bar internally. Bob Fenner>

Locate Obsidian Rock for Japanese Dry Garden 10/16/05 Robert, my name is James Russell and I am trying to find a location to buy some Obsidian rock for my Japanese dry garden. Any ideas or leads that you can impart my way would be greatly appreciated.  Thank you for your help.  <Mmm, the best source or link to it is through local "Rock, sand, gravel outlets" (you can likely find through the Yellow Pages... under "landscape")... if they can't help you, I'd ring up the clubs in your area that deal in "Minerals and Gems"... they will know where to even collect this volcanic glass... Do be careful (of course, gloves) in handling... obsidian is very sharp. Bob Fenner> 

How to make faux pond rock look more non-faux 8/2/05       I have some artificial rocks that I have used to put in and around a garden pond. These "rocks" have holes in them and I have used real ones to try to fill in the holes so as to not have unsightly gaping things in my rock wall. I need to cover another area with these same kind of rocks and would like to know if you have any ideas about covering holes? The rocks are made of some light weight fiber (I think) type material and they are plastic on the back side. <Mmm, likely CRF's... concrete reinforced fiberglass...> The back of all of them is flat. I tried the form spray stuff that you use around pipes but that stuff never set up and I poured it right out on the ground! I have racked my very old (probably worn out) brain and can't come up with a thing!! Any help you might offer will be greatly appreciated!! Thanks Candi Rivers   <Heee! We never made these types of faux rocks, but installed many of them... reasonable additional material can be added... fiberglass cloth, resin and hardener... and some sort of "matching" substrate (sand, dirt...) while all is setting up (use your funkiest clothing, gloves...). The cloth is best cut with sharp scissors and the resin/hardener painted on... with an inexpensive to-be-thrown-away brush. Oh, and cementaceous material does not stick for anytime in these applications... Bob Fenner>

FAQs on Water Feature Rock Use/Making Mr. Fenner - I'm no expert, but the time seems right for a well written waterfall publication.  I've spent a great deal of time researching my waterfall/stream rehab program and while information is available, credentials such as yours are not available.  Greg Bickal ( http://www.bickal.com) sells an inexpensive DIY CD, but my 30 years as a commercial banker has left me overly skeptical of anything that not tried and true. <Am as skeptical...> Anyhow, if you need some help from someone with pretty good grammar and reasonable word processing/page layout skills, I'd be willing to help. -Barry <Outstanding. Thank you for coming forward... at this juncture, I think Jason (Chodakowski) and I's efforts at a small water feature (design, construction, stocking, maintenance) are about all we and the intended audience can/will handle... I do wish there was a simple kinetic pictures method of showing folks the "how" of different types of artificial rock making... the sounds that can be engineered... some of the philosophy of rock placement... Bob Fenner>

FAQs on Water Feature Rock Use/Making Instead of the reference to http://www.rockandwaterscapes.net/, I wonder if you intended http://www.rockwaterdesigns.com.  They're located in Yorba Linda (vs. Ireland) and seem to specialize exclusively in the use of glass fiber reinforced concrete. <Nice site... don't know what happened to the Rock and Waterscapes that used to be in California... don't see it on the Net> I'm trying to resurrect a concrete stream and two waterfalls in my front yard and am grateful for the wealth of useful information contained on your site.  Thanks! Barry Moore Fullerton, CA <Thank you. With a friends help at layout, editing, am trying to turn two self-published waterscape manuals into a useful tome... with more graphics, examples. Bob Fenner>

Waterfall article on WetWebMedia.Com I was reading your article on WetWebMedia.com. I have a boulder waterfall going to my spa. They used granite for the areas where the water flows but holding up the spillway are large (sandstone) boulders. After a few years, one of the boulders is crumbling into sand and it falls into the spa as the ants crawl over it to carry off the grains. I tried Thompson's on it and I tried other water based sealers from Home Depot but they don't last long if it rains. Do you have any "brand" or "type" recommendations to slow down the "erosion" of my boulder (5 foot round) ? Any suggestion based on your experience would be greatly appreciated. <Thompson's doesn't work. Mmm, can't think of the brands right off hand, but do know where I would call on re in San Diego: Expo Stucco, in the Miramar area. Bob Fenner>   

Indoor Koi Pond Question/Problem Hello, I've been browsing your site FAQ's for about and hour and haven't found anything that resembles my problem yet. Hope you can help. I have an indoor Koi pond that was here when I bought my house. I've killed many a fish, but the pond has been stable for about 2 years now and I thought I was out of the woods. I have two Koi that were about 2 inches when I got them, about 3 years ago. One is now about 14 inches and the other is maybe 9-10 inches now. About 2 weeks ago, I bought some river rock to put in the bottom of the pond for some "interest". I boiled them (the rocks)... <Heee!> ...and dechlorinated them before I put them in the pond. Now, I have round white spots appearing on the pond liner. They aren't slimy, or hard like calcium deposits and I have no idea what it is, but they do seem to be multiplying.  <Mmm, perhaps freshwater sponges... maybe only a bit of residue from the rocks presence> The water temperature gets pretty cold in the winter (it's built into the floor, the house is on a slab so it goes right into the ground. My guesstimate is that it is about 250 gallons) and Blackie and Whitey have been 'lethargic' but I attributed that to the temperature. <Reasonable> They don't go anywhere in the pond without each other, and prefer to hang out at the bottom near the secondary intake of the filter (It's a biological filter with 5 chambers). They've never been social Koi, don't eat out of your hand or any of that jazz that I read about, but they seem more active when it gets dark. Blackie has a small white spot on his skin. It's not a bump, does not look like wax drops, he does not look like he has been sprinkled with salt. The pond readings are:  Ammonia = 0  Nitrates = .50  pH = 6.5  Salt concentration is .06%. I initially thought this was "Ich" and added about 2 cups of salt about 8 hours ago. <Good idea> I'm planning on packing the kids up in a cooler for a trip to the Fish Store to see if they can diagnose the spot, but I can't bring the pond liner with me. I've attached some pictures, but I don't know that they will be of any help to you. Any ideas? Thanks in advance for any clues.  Nancy Hart <I would take some of the rocks out... and soak them in water of known make-up (like reverse osmosis if your tap has a great deal of dissolved solids)... and measure for changes in pH, alkalinity over a week's time... Boiling the rock et al. would not change its basic chemistry... If it were me, mine, I would remove the rock in the pond, until the testing is done. Bob Fenner>

Rocks for scenery Dear Robert, We are looking for ways to make large, but lightweight, rocks and boulders for set designs for church programs. My husband recalls hearing about a mixture of Styrofoam (?) and concrete. Do you have any idea's? We are looking for something for this Easter- fairly quick- but also for Vacation Bible School this summer and future projects. Any advice would be appreciated.  Thank you, Bridget Marotz <Mmm, something of size? Temporary? This might better be built of canvas bagging draped over a frame of wood, tied rebar-steel... and spray-painted to look rock like... More expensive and permanent/sturdy would be two-part foams with cementaceous materials sprayed over them (with color)... and these last can be tooled to be more realistic... how permanent, how big a project are you considering? Bob Fenner> 

Fake rocks hi bob, have just read your postings and found it very informative. you see I have been researching how to make fake rocks with spray polyurethane foam and elastomeric coatings. <Mmm, used to do this... about twenty years ago. The field must have progressed by now...> we have this neat little spray unit for waterproofing and it will also spray foam. <Yes> my plan is to line the sculpted earth (watercourse) with the foam (6lb density) I was going to then cover the foam with our fast Set elastomeric membrane then in some area's I want to  try and make it look like a real rock or rocks waterfall etc. <Yes... Perhaps with some "structural element/s underneath". That is, wire bent into shape, perhaps tied, and possibly steel-rod (rebar) with it if the "rocks" are very large). And, oh I see you ask the relevant prompt below> what do they put over the fiberglass to make it look like real rock. <There are dyes (for fiberglass as well as concrete, mortar use) and "spray" materials that can be applied to give more of a "sparkly", different "rock-type" exterior appearance. I encourage you to check with the concrete and stucco suppliers in your region/country.> any advice would be appreciated. mike <Bob Fenner> Michael Grosman

Fiberglass Boulders Do you know of anyone who makes fiberglass boulders that could be lifted off of or which open up and close to cover utility boxes? <There used to be a bunch of folks (ourselves included) who made these. Let me check the Net... Oh yeah, Rock and Waterscapes is still in business: http://www.rockandwaterscapes.net/ If they're not able to economically ship you, ask them who is in your area. Bob Fenner> Paula Southman Platte City, MO 
Re: Fiberglass Boulders
Thanks for your reply. I think their boulders are made of concrete and so would be too heavy for the purpose. If you think of anyone who carries fiberglass boulders, please let me know! Thanks again. <Please do contact these folks... they used to make "CRF" (Concrete Reinforced Fiberglass) boulders... which are actually not that heavy, and stand up to weathering and human interaction better than just fiberglass and resin... Our old companies used to make both. If Rock and Waterscapes doesn't make lightweight faux rockwork, they will know where to send you next. Bob Fenner> > Do you know of anyone who makes fiberglass boulders that could be lifted off of or which open up and close to cover utility boxes? > <There used to be a bunch of folks (ourselves included) who made these. Let > me check the Net... Oh yeah, Rock and Waterscapes is still in business: > http://www.rockandwaterscapes.net/ > If they're not able to economically ship you, ask them who is in your area. > Bob Fenner> > Paula Southman
Re: Fiberglass Boulders
< Thank you for contacting Rock and Waterscapes, we are based in Ireland and only serve the European market. The only company I know of that would be able to help you is John Groark and Associates Inc in Honolulu, their web site is : www.groarkco.com <Thank you for this input. Will post on our principal pond site, WetWebMedia. Bob Fenner>

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon

by Robert (Bob) Fenner
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