Desert climate + Hard Water ??

[Pete]

Hi guys,

First time poster, a big howdy to all.  

In my new home, I am tempted to build an aquaponic system for vegetable, ie fishes to support plants. The new house being in California desert near Palm Springs, I am not sure if the climate and water quality are suitable. 

Climate:
Desert climate, very dry except Aug/Sept during the so call monsoon, it gets a bit humid. Detail
Super hot summer July-Sept. day time can reach as high as 125F+ (50C+) and night time around 100F+ (37C+).See its temp today.
Mild winter day time around 80F (26C), night 40F (4C) with occasion

Water:
·Range for pH is 7.3 units to 8.2 units with an average of 7.8 units.
·Range for Hardness (as CaCO³) is 23 milligrams per Liter (mg/L) to 290 mg/L with an average of 120 mg/L.
Detail

My worries:
Water too hard to support growing plants? Summer being so hot, how to keep water within reasonable temp for fishes and plants. 

I want to build a small pond say 6'lx3'wx3'd in my side yard (20ft x 8ft). Above ground but under shade. As for plants, mainly asian vege, lettuce (too hot?) carrots, tomatoes and cucumbers. Nothing exotic.

Thanks for reading and helping.

[TCLynx]

My water is hard too and it can be a bit challenging to keep the nutrient levels all in balance when dealing with very hard water.  Using an RO filter for at least some of your water use/top ups may be an appropriate way to go, especially during the hot season.

 

During hot season you will probably not only need excessive shade for the fish to stay cool but probably also a good amount of shade for the plants.  Luckily evaporative cooling can be effective in the desert though it would mean needing some extra water for the system.  Go large on the amount of water (do you have room to make the pond larger?  I'd go for more like 700-1000 gallons just for temperature stability) and you may perhaps need to do constant flood through the summer to avoid picking up too much extra heat through the grow beds doing flood and drain.  Perhaps if you can design the switch over easily, then doing constant flood to the grow beds for the daytime and switching to flood and drain overnight you might be able to shed more heat at night at least during the dry season.

 

Summer probably will be a bit extreme for lettuce but I've found that lufa can grow you a beautiful shade cover and it seems to thrive in the heat.  You can eat the small fruit and let some grow big to make sponges.

 

Good Luck, with a bit of creativity you can probably manage it.

[Pete]

 

Thanks TCLynx for your advise.

Let's see if my understanding is correct:

1. When water evaporate, all the minerals in the water do NOT evaporate with the water.  So the remaining water gets even harder, unless using RO water as replacement, the water gets harder as time goes on.

2. However, fishes activities, plants decay etc. trend to produce some acidic matter which soften the water.

3.  One wonders if 1. and 2. neutralize each other? If 2>1 then the water will soften over time.

3.  I understand operators of  established aquaponic systems do not change water often if at all.  Just add top up to counter evaporation?

 

I have tried to grow submerged aqua plants in my cichlid plants with minimum success ie slow growth.  African cichlids prefer very hard water but plants don't.   Don't want the same to happen to my veges.

TCLynx said:

My water is hard too and it can be a bit challenging to keep the nutrient levels all in balance when dealing with very hard water.  Using an RO filter for at least some of your water use/top ups may be an appropriate way to go, especially during the hot season.

 

[TCLynx]

Yes aquaponics and the bio-filter activity tends to lower pH over time but yes evaporation just takes away the water leaving the excess minerals so you would probably need to use de-mineralized water to top up at least part of the time.  If you have kept fish, you know you don't really want to start out with completely demineralized water but the plants would prefer that you don't totally encase them in calcium carbonate.  At least most plants.

 

That said, I have hard water and I even have a system that is full of shells.  That systems has iron deficiency problems and potassium lock out due to an over abundance of calcium, however, watercress actually seems to love it that way and there are some other plants that have done scary good in it too (Banana.)  Lettuce doesn't seem to mind too much provided the weather is cool enough and I did really well with broccoli and such this past winter and the tomatoes, eggplant and water chestnuts seem to be thriving despite the problems.

 

Sometimes you just gotta try a few things and see what works.  And over time the system will mature and change.  Some things that really didn't do well for me the first year have done far better this year.

[Pete]

Thanks TCLynx, sounded like I will have more issues with the desert heat than hard water.  

 

BTW, do you know where one can buy barra fingerlings in the US?

[TCLynx]

I don't know if they are available here at all.  You will have to do some research to see what is allowed in California.

[Pete]

I saw lots of live swimming barra looking fishes (quite sure that they are barras) for sale in Asian supermarkets here.  normally about 12-14".  Just don't now where they come from or where to get fingerlings.  

 

I think the desert is warm enough to raise barras year round.

[Chris McMahon]

I live in Palm Springs if you want to see my system. It's doing good considering the hot weather.

[Pete]

Hi Chris,

 

DEFINITELY would like to see your system.  I just left the desert 3 days ago but will visit again in Aug. I'll contact you a week or so before I start driving down.  BTW, what do you grow? and do you grow them year around?

 

Thanks
Pete 

[Chris McMahon]

Hi Pete,

I just setup my system in May, just got my starting fish in July, I am running tilapia becuase they don't mind the high PH.

Right now I don't have a green house yet. I am doing well on green peppers, grapes, cherry tomatoes, watermellon. wheat grass, and others. I expect the system will take off like a rocket when it starts to cool off a bit.

 

[Pete]

Do we need green house for the desert ?  To keep out of pests or as weather protection?

[Chris McMahon]

I am sure it would help. They are not terribly expensive. I am deciding if I want to make a greenhouse or a dome.

[TCLynx]

In your hot climate, you may find something more akin to a shade house better unless you find the dust getting into the system to be a problem.

 

I find in my climate, a greenhouse is more trouble to me than it is worth for a non commercial operation.  For my backyard systems I find a bit of shade more useful half the year and then take the shade down and grow cool weather crops in the winter and I have fewer problems with most pests (other than squirrels) without the greenhouse.

 

If you go greenhouse there you will definitely need to put much thought into keeping it cool and ventilated most of the year.