Natural swimming pool

[Jon Parr]

So I've been planning a natural swimming pool for the last six months, and I'm ready to break ground. Also called a swimming pond, the idea is to use natural plants and bacteria to keep your pool chemistry in check instead of chlorine. I've got a few basic principles I'd like to design around, would love some feedback.

1. First and foremost, swimming is of primary importance
2. O. Mossambicus planned for fish stock, and perhaps plecos
3. Pool will be 30' x 30', depths are negotiable
4. There is several thousand sq. ft. available for grow beds both above and below pool grade
5. Pool and grow beds will be heated, and covered with an atrium (fancy word for greenhouse)

[Jon Parr]

Questions for the pros:

1. I plan on surfacing the pool with a product called Pebble-tech, or Pebble-sheen. It is a pebble and modified plaster, where more stones are exposed than plaster. I want it dark, like black or blue, partly for solar heat, partly to disguise the off color of the water. Any knowledge of pH stability with this stuff, and best color to use?
2. I'm sold on the anti-algae properties of barley straw. It works, apparently, by producing lignen, which in the presence of sunlight produces hydrogen peroxide to battle the algae. Does the presence of lignen and h2o2 also battle the benificials in the media, or is it safe since it is dark?
3. Any suggestion on stocking densities to maximize fish production and still have inviting water? I'm guessing 1 lb. fish per 50 gallons.
4. Any tips for controlling bio-slime on pool surfaces?
5. Conventional natural pools favor marsh plants, of course I want edibles, or perhaps fodder crops for other animals. I would like to go heavy on grow beds, so that the returning water is truly clear and clean. I envision planters snaking through lounging areas with lush grasses, grains etc. Some would have media and permanent plants conducive to pool lounging, like grapes, papaya, passion fruit, citrus, and strawberries. Fodder beds would have no media, just roll out a mat of grass and replant, maybe a jute roll to hold the seeds in place?

[Jon Parr]

Also, I seem to have the greatest difficulty keeping detritus off the bottom of my fish tanks without some periodic house keeping, and that issue would be magnified in a pool. I consider myself to be overly ambitious, but I strive to be lazy. It's my dream. So regular manual maintenance is to be avoided, by good design, and or automated devices. So far the cleanest FT floors in my AP systems are ones with bottom suction and large rocks to cover piping. The detritus is still there, but it quickly falls to pockets out of sight. I am thinking the best floor for the pool would be 3" cobbles over a network of 2" perforated pipes with good suction. I want the fish poo to be drawn below rock level like a magnet, not wafting around finding pool surface to cling to.
I'm fairly certain that I can figure a system suitable to swim in with no fish, but I'd sure like to swim with the fishes.

[Chi Ma]

I'm pretty lazy when it comes to cleaning the fish tank. So I bought some bullheads that keep the tank bottom stirred up so that the pumps can suck up the sediment.

[Jon Parr]

Hi Chi, thanks for that. Bullheads that I'm familiar with are saltwater with semi-venomous spines on there heads, could make for exciting times while wading in the pool. I'll look up the freshwater kind that you must have. I have plecos in my AP tanks, they do a great job of cleaning as well, but again have quite an array of spines, and tend to chill in the corners during daylight. They don't move until you touch (step on) them. I'm in Santa Cruz, and you're in Saratoga, right? We should meet for a beer. I lost my adult red claws about the time I read that you lost your babies. My only survivor was a berried female moved to a different tank. So now I have a couple hundred 1" long red claws, but only one adult female. Maybe we can swap some, eh?

[David Waite]

Jon in regards to natural swimming pools or ponds I can tell you what my research has found out as well. In regards to question 1. Pebble tech is really for non skid or pool deck surfaces. Havent seen it used for in water application so cant speak to that. I would use a ferrous cement or gunite and cover with pool plaster or paint with pool paint. I am using the later due to expense and easy to repair and aquaculture safe. Europe has been doing this for 15 years and has a 30 percent bio filter to swimming volume ratio to keep the water clean. The pond will bio slime and there is no stopping that. There is no formula for fish ratios in swimming ponds so you are in uncharted territory. I think you will need to double gravel media to 60 percent of pool volume with light stocking 1 fish per 50 gal to keep it under control.

Jon Parr said:

Questions for the pros:

1. I plan on surfacing the pool with a product called Pebble-tech, or Pebble-sheen. It is a pebble and modified plaster, where more stones are exposed than plaster. I want it dark, like black or blue, partly for solar heat, partly to disguise the off color of the water. Any knowledge of pH stability with this stuff, and best color to use?
2. I'm sold on the anti-algae properties of barley straw. It works, apparently, by producing lignen, which in the presence of sunlight produces hydrogen peroxide to battle the algae. Does the presence of lignen and h2o2 also battle the benificials in the media, or is it safe since it is dark?
3. Any suggestion on stocking densities to maximize fish production and still have inviting water? I'm guessing 1 lb. fish per 50 gallons.
4. Any tips for controlling bio-slime on pool surfaces?
5. Conventional natural pools favor marsh plants, of course I want edibles, or perhaps fodder crops for other animals. I would like to go heavy on grow beds, so that the returning water is truly clear and clean. I envision planters snaking through lounging areas with lush grasses, grains etc. Some would have media and permanent plants conducive to pool lounging, like grapes, papaya, passion fruit, citrus, and strawberries. Fodder beds would have no media, just roll out a mat of grass and replant, maybe a jute roll to hold the seeds in place?

[John Jay]

I used to scrape slime and barnacles off of yatchs, the arguments were that blue paint was best because of higher copper content,,, but i painted mine black because no one paid me to srub it and I wanted the least slime.  Algea grows on dark colors slower and often green algea prefers lighter colors and browner algea prefers dark the bonus is brown is easier to remove.  . So go dark

 

As far as fish I recomend pirahanas,,, just kidding  if its warm enough use irredessant cats (shark)  or basa they grow super fast eat anything and when I work at the aquarium  they never ran into me in murky water because of there huge eyes and good  lateral line navagation.  unlike the pacu  dangerious to swim with  because of the size and dense skull tissue,  been ramed a few times

[Jon Parr]

Thanks David. I just typed a lengthy reply to you, but somehow I lost it before I posted. Damn. Anyway, are you also building a natural swimming pool?  I'd like company on the project. I've only seen pebble-tech used below water line. It is applied like plaster over gunite or shotcrete, and then abraded with a buffing wheel hooked up to weed-whacker, to polish and expose the aggregate. The advantage is that the actual color of the pebbles used determines the finish color, and is much more colorfast than plaster. Paint is probably an excellent option for price and colorfastness, but not nearly so elegant. You're probably right about the bio-slime, but I'm hoping the barley straw will help there too. 
Thanks John Jay, sounds like a dark color may be an unexpected boon. I wonder if that is simply because a light surface would reflect more light, thus feeding the algae. Not sure how to take your fish suggestion, though. I think the only flesh-eaters I want in the pool are my kids. 

[TCLynx]

Perhaps to an extent the dark color just helps to not see the algae very well too.

 

If the set up will be in a greenhouse, then the only leaves/debris are going to be from the plants growing in the system and the people who might leave things around.  Perhaps an automated pool vac would be the way to deal with debris in the bottom of the pool?  Anyone used such a thing with fish in with them?  Is there much danger of the fish and Vac not co-habitating nicely?

[Jon Parr]

Good idea about the pool vac, TCLynx. I would imagine since they move along slowly and random, the fish would probably just keep their distance. Curious how the vac would navigate the cobblestone. Curious also how the vac would do in a normal large AP FT. Hmmm.So I think it prudent to try an intermediate project. I've got an 18' by 4' circular above ground pool. It is currently chlorinated, but it is near the end of swimming season here, and I think I can convince the wife to agree to an experiment. The 18' tank is about 7000 gallons, and 250 sq ft. SLO drain to 5) 8' x 18" wading pool gravel GBs, that will auto-siphon to a 8' x 18" sump pool, that will contain barley straw in mesh bags, and a toilet fill-valve to maintain water level. May as well throw a pool vac in there too, to settle that question. At my assumed 1 fish per 50 gal, that comes to 140 fish. Low density for sure, but enough to know you've got company. Biggest problem for experiment's sake, is that there is no way I'm putting all this in a greenhouse. Too much work for temporary run, and no room to leave it long term. So how 'bout a bubble cover like some pools use. Should work if plenty of air is pumped in under the cover. Alright, next week I'll set it up, take some pictures. 

[Harold Sukhbir]

Hi Jon

I want the fish poo to be drawn below rock level like a magnet, not wafting around finding pool surface to cling to.

 

My pump is at the center bottom of a circular FT. The water enters the tank by gravity in a clockwise direction. This design was deliberate to create a vortex to migrate all debris toward the suction in the middle. My experience is that it works well, in fact, in the past 8 months, I've brushed with a broom only once, and that was at the beginning, I've never cleaned since, so this design is really self cleaning. After reading about your intended AP/swimming pool I have to mention that when I feed the fish they release poo into the water straight away, and this starts circling the tank, at the surface, following the current, but it takes a good 30-50 minutes for it to slowly sink to the level where the pump finally sucks it up. In your case I believe it will float for the same length of time.

 

Maybe you can design a rectangular pool with suction and inflow at opposing ends, suction preferably ending in a pocket made inaccessible to humans and inflow where you enter for bathing. 

[David Waite]

Jon on the pools in Scandinavia and Germany the pool bottoms are course sand on the wading end and 1 inch round rock with suction under the rock in the deep end. This gives a larger bio filter without having to make the pool so large. If you went this option I think your algea growth would be confined to the sides and shallow areas. Have no experience with your pepple tech. We use a product like that on pool decks that is epoxy based and spread on. The whole idea to swimming ponds is to get away from pool vacs and the filters ect...ect... You are cleaning the water through gravel media and plants. Filters and pond vacs are what you are trying to avoid. You will have a surface skimmer with a catch basket to help with insects and leaf debri and thats about it. Three suction points are the norm. Surface skimmer, Bottom suction under about a foot of large round rock and then shallow gravel bed suction in your side or plant growing area. This is just one way Im sure there are lots of different configurations. Some add air as well. Not sure if I am going to do that. I plan on building one but will have to get through obamanomics first. hehe.

Jon Parr said:

Thanks David. I just typed a lengthy reply to you, but somehow I lost it before I posted. Damn. Anyway, are you also building a natural swimming pool?  I'd like company on the project. I've only seen pebble-tech used below water line. It is applied like plaster over gunite or shotcrete, and then abraded with a buffing wheel hooked up to weed-whacker, to polish and expose the aggregate. The advantage is that the actual color of the pebbles used determines the finish color, and is much more colorfast than plaster. Paint is probably an excellent option for price and colorfastness, but not nearly so elegant. You're probably right about the bio-slime, but I'm hoping the barley straw will help there too. 
Thanks John Jay, sounds like a dark color may be an unexpected boon. I wonder if that is simply because a light surface would reflect more light, thus feeding the algae. Not sure how to take your fish suggestion, though. I think the only flesh-eaters I want in the pool are my kids. 

[Jon Parr]

Thanks Harold. I'll play around some more with currents in a rectangular pool, and a circular pool is an option too. I figured it best not to swim at feeding time anyway, and plan to experiment with a very slow feed auger that drops food all day. I've also noticed that when I feed floating pellets, the poo tends to float as well. I have one tank where I feed algae scraped off my breeding tanks, and that poo is dark green and settles quickly. 
Thanks again, David, but in my case I'm more concerned with getting rid of chlorine than eliminating pool vacs and filters. The grow beds should serve as suitable filter, and the pool vac, if it is needed and effective, is a minor evil. They are powered by suction, and are really no more complicated than simply plugging in to a pump already used for that purpose. I am curious to see how they would work in AP in general. They certainly would keep any neglected corners from going anaerobic. Aside from chlorine, my other motivation is simply to double purpose my land and resources. It seems like, for about the same materials and effort, I can have both swimming pool and garden, and a more enjoyable swimming experience. Money saved on chlorine, shock, algaecide, filters, etc would probably go a long way in buying fish feed.