Backyard Aquaponics
A place to discuss aquaponics

Hi, I'm new to the forum but have been reading a lot on here about different kinds of liners and ideas for the stock tanks as well as the grow beds and I had a few questions. Everyone and their mother has opinions on which is the best but I had a specific setup I'm looking at and I think it requires a specific answer.

I want to build a small pond in the back yard, roughly 300 gallons, and run a series of 3 or 4 grow beds off of it on the patio cement. I was originally going to use a tarp, from Home Depot that was 12x16 and made from 10mill polyethylene but when I saw that it shouldn't be on painted surfaces for extended periods of time I kind of got scared. I've heard PVC is one that a lot of people use but still a lot are aleptical because of chemical leaching.

Here's my idea...I am planning on getting a 10x12 PVC that claims it is plant and fish safe for 64 bucks, then purchasing a large unbrella, the kind for outdoor tables, to place overt it to prevent sun and rain from getting in ( in Florida it rains too much to let all that rain water fill the system). The backyard only get afternoon sun anyways, and te pond would be against the house, so with this setup, the pond will only get the Florida sun from about 4 or 5 in the afternoon til about 7 or 730. I'm thinking that will greatly help with the UV deteriation and heat factors and make the PVC perfectly safe.

Is this a plausible idea? If so, would it be safe for the grow bed as well saying as any part of the grow bed that could possibly leach bad stuff into the water will be covered by media? Thanks for the advice! And of this answer is already somewhere please just link it to me. I've been researching this stuff for a whole but have never been able to find a straight answer.

The PVC liner/tarp you are talking about is just about the worst you could chose. The chemicals in PVC that you need to be worried about are the ones that make it flexible. Hence rigid PVC pipe is safe but flexible PVC liners are not. Those thick tarps are full of the stuff because you need more of it to make the thicker PVC material flexible.

Having said that it is very likely it will be fish and plant safe however, the chemicals are HUMAN hormone analogues not fish or plant hormone analogues which is why they worry me.

Having said that the leaching you get from a liner will be less than many other things that you may have in your house for example fire retardant chemicals in any new furnishings you may have in your house (by new I mean less than 5 to 10 to 15 years old (the older the less chemical remains but there can be still quite a lot in oldish stuff 5+ years)).

First of all, thanks for the responses! Secondly, this is the second time I am typing this out because the page froze, so ignore punctuation mistakes and it may be a bit more concise.

To answer and respond to your bolded comments...

1. I would like to make a series of growbeds, meaning multiple that are receiving water in unison. The reason for that is because if I fill one big grow bed, the water level will change too much. So i can push the limits of the typical ratio of grow beds just a hair by making multiple growbeds in which the water is draining back into the pond at different intervals (or the same, just offset so as to not displace such a large amount of water at the same time). The pond will be roughly 300 or more gallons, so i was hoping for about 35 to 40 gallon growbeds, and most likely 3 of them.

2. What is a good pond liner? And let me clarify that I am not planning on using the tarp anymore. What I was referring to in my actual plan was a PVC pond liner, this one to be exact...

http://www.homedepot.com/p/Beckett-10-f ... /100030118

which claims to be food and plant safe. Now I understand that PVC releases certain chemicals when in direct sunlight and more so when it is heated, but that was the idea about the umbrella, which, to answer your other question, would be pulled down during the winter when the UV index drops here and allowed to warm the pond up a bit (i also plan to buy a water heater for freeze warning nights). But in the location it is at, with no umbrella, it would start getting sun around noon and for the rest of the day.

3. As for the media question, it was because I was thinking if the answer to the pond was a yes, then would I need to be worried about the grow bed saying as none of it will be exposed to sunlight. That is to say, if the pond will not be a leeching source, the growbed shouldn't either because the liner will be covered with media.

My problem with all of this liner stuff is that it seems everywhere I go someone hates PVC and someone loves it, and someone will hate EDPM and someone will love it, and others will use garbage packs, and some concrete. I am really looking to do it on the cheap, and maybe I tricked myself into the hobby because the first time I did it, I used a large plastic storage container for both the growbed and the fish tank, and it worked really well, and I may have been poisoning myself the whole time. But in any case, I really want to see a large set up happen, just not if it will cost me 150 bucks for just a liner and even more for growbeds and other equipment.

Thank you so much for your help and suggestions, and I know that we will be able to come up with some sort of solution!

They give off chemicals faster when heated but even in cold water not exposed to sunlight the plasticisers will leach into your water.

Liners made from EDPM, HDPE, LDPE, LLDPE, polyurethane and bituminous are they way to go. Many people use EDPM liners TCLynx has lots of photos in her thread showing the use of LLDPE liners. HDPE liners are veyr tough but that can be a drawback because they are not very flexible. Polyurethane liners are very good but relatively expensive as are bituminous liners.

From all my research the cheapest way to build a large system with GBs where you have to buy the materials is two large GBs lined with a quality liner. Large GBs are cheaper to build and plumb rather than lots o little ones and you need less materials because their volume/surface area to wall ratio is less which means cheaper.



There are opinions everywhere and each liner material has pro and cons. As to poisoning yourself I would never recommend using a PVC liner but honestly if you have even vaguely new furniture or a new car then the dosage you get from them probably far exceeds the dosage you will get from your system.

Haha well thank you for the info and suggestions!!! And I'm laughing because as I read that last line and with the research I did tonight about the leeched stuff from PVC, I'm think the amount of that crap that is my system right now is far beyond anything I'd pick up in my setup, saying as I use plastics of all sorts every day, and apparently the average person has some in the system all the time, and again I read that poultry is supposed to be a super high source of that stuff. Looks like I might have to start buying green wise chicken from publix soon. But thank you again for the info. I'm gonna go to the local hardware stores around here again and see what I can find. I'll post an update of my decision, but if you or anyone else think of something, please let me know! Thanks again!

Everyone has some and the average people have lots.

There is a book out there where the author sent her breast milk off for testing and got a serious shock reading the results. With a lot of effort she was able to drastically reduce the chemicals in her breast milk and presumably the rest of her body.

So I made my decision. First of all, it looks like someone in my church is just getting into aquaponics big time and has some dura scrim to sell me, so I will most likely be purchasing that to keep on hand for later. And by most likely, I mean I will have to talk that over with my fiance first. Secondly, I decided to go for an IBC container and do the aquaponics conversion to it. It just seems to be too good of a price at $50 to pass up. It's a decent grow bed area, and I will probably start with one and move onto two in the near future. I have a friend who has purchased from the guy before as well and he said it was legit so that makes me feel better about the purchase. But thanks again everybody for the insight, and please let me know if there is anything i should know about the IBC containers other than that they usually have had chemicals and such in them because I know to look for that. Thanks again!

Oh and yeah I plan to use the dura scrim later on when I possibly make a custome grow bed for the two IBC. Its I beleive 6x12 ft which could definitely be used to make a 2 decently sized grow beds later on down the road.

Sorry to double post, but I am just not realizing that the ratio for grow bed to fish tank is 1:1!?!? When I first did my system I did 1:2, grow bed to fish tank, and I thought that was the ratio. That's why this whole time I have been trying to get a 300 gallon pond to only run 100 gallons of grow bed.

So with a small pond, 100 gallons or so, I could easily run 75 gallons of grow bed? And with an IBC, could I run about 200 gallons of grow bed with a 275 gallon tank?

And I am guessing the reason i can be 1:1 is because the media takes up so much of the space in the grow bed?

Ratio is more like the other way. 2:1, GB to FT.

Wow well doesn't that affect the water level pretty drastically? In the fish tank, I mean. Or does that usually mean you run multiple grow beds so that the siphons are activating at separate times?

Ok Stuart, you got yourself into that one.

What do you mean Sleepe?

It can depends on how you design your system. Lots of way to do things so that the water levels don't change that much without having to synchronise GB flooding and draining. The easiest way is to have a big sump.

Whats a sump?
How does it fit in the system?
Whats the alternatives to a syphon?
What sort of F&D?
Why does the ratio have to be 2:1?
etc etc
You are well, not necessarily nice, but sometimes a little too helpful.

The topic was 'Pond liner confusion'.

If I need help Stuart, I hope you will not hold this post against me.