Aquaponic Gardening

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Hello everybody,

I've been reading for hours and hours about all of your systems and questions.  I have been interested in aquaponics for a couple years now but never really knew where to start.  I read Sylvia's book, which I got for my birthday, over the last week.  I just HAD to get started after reading.  So I got myself a bunch of hydroton and a 600 watt HPS yesterday.  I'm having an IBC delivered hopefully Sunday.  I'll be setting up in my garage, because unfortunately I live in a Quadplex with almost no yard and crippling HOA style regulations.  I'm planning on simply cutting the top foot of my IBC off for a grow bed.  I'm pretty set on a simple flood and drain system mainly because I cant afford to damage the garage should something fail.  So I went with the simplest design which will simply drain back into the fish tank should my pump fail.

Anyway I have a couple questions that I would love to hear some input on; 

1. Are tilapia going to be too difficult to keep warm in a 1 car garage near Denver?  I will have the 600 watt HPS running in there.  I talked to the housing office here and they want me to ventilate by opening the garage for like 20 mins or so everyday. Am I gonna be fighting a difficult battle with tilapia?  I am certainly willing to get a tank heater but I don't really want to be running it all the time.  I am definitely trying to come up with ideas to insulate the tank too.

2.  I read in the book that a mag drive pump is ideal.  I have been looking at pumps and I just don't really know what exactly differentiates some from others.  Are some better for pumping solids like fish waste that I should be looking for?  Also I understand oversizing the pump because I will need to pump the water up to the grow bed, but does the vertical distance start at the top of the water or would it be down where the pump is on the floor of the tank? Say around 5ft versus 2ft or so.

Thank you all so much for providing such helpful content I feel like I've already learned dozens of lessons in the past week or so I've been lurking here.

Daniel McElhattan

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I'll leave others with Tilapia experience to answer your first question David.


With regards to pumps, indeed you should be looking for a pump that can (typically) pass 5mm solids.


Often they're referred to as "dirty water" pumps.


The "head" of a pump... is determined by measuring from the top level of the water in your tank.. to the height of the outlet in your grow bed...


The "head" also includes the restrictive forces related to the length of any plumbing, and fittings... these can be hard to determine, but information on how to calculate these factors... are often provided on good plumbing sites...


In simple systems, this "head" will generally not be significant, and can be essentially ignored.


You need to select a pump that can effectively turn over the volume of your fish tank once per hour.. as a minimum...


And I would suggest that you actually source a pump with at least twice that capacity.. to allow for expansion if nothing else.


If the pump you source has too much, or excess flow... you can always tee off and redirect some of the flow (use a ball valve)... back directly to the fish tank... via a spray bar... for extra oxygenation...

About your pH problems.

I answered with this the other day....

I would probably add some calcium carbonate and/or potassium bicarbonate to buffer your pH up into a readable range, like 6.5 just so you know it isn't way low, either that or get a pH test that will tell you what the pH really is when it's below 6.

Calcium carbonate (lime, shells, limestone or marble chips, chicken grit)  Put some in a bag and place it under the water flow or in the fish tank for a slow acting buffer.

Potassium bicarbonate (find it at brew and wine making supply shops or online) is a bit faster acting and a source of potassium.

In a pinch you can even use baking soda (be careful here it is fast acting and you don't want to use it except in emergency since it will add sodium to your system which the plants don't really want that much of.

You only want to move your pH a little bit per day but since we are seeing ammonia, I'm worried that your pH may already be too low.  If you have hard tap water or well water, then simply topping up the system with the hard water may help bring your pH up.

Daniel McElhattan said:

Siphon has been running stably for over 24 hours.  Did my first water test PH is reading bottomed out at 6.0.  Should I be raising this somehow?  I am cycling with 15 small goldfish.  Ammonia read .25 ppm. I'll be adding a few plants tomorrow most likely.  The goldfish have been in since Friday night.  I didn't test nitrates tonight.  When Do you think I should start testing for nitrates.  I am cycling from scratch.  I have been feeding every few days so far a little bit cause I don't want the ammonia to get out of control.

Does anyone have any ideas as to how my ph got so low in the first place,  It comes out of the faucet at 7.6

Vlad actually explains it really well, so maybe he will pop in with a link to one of the places he has done that.

But anyway, the bacterial processes that convert the ammonia into nitrate actually use use up the buffering capacity of your water and the pH naturally drops over time.  It is totally normal to need to add some buffer to your system.  Many of us will alternate between a calcium buffer like calcium carbonate and a potassium buffer like potassium bicarbonate.

There are faster acting/stronger pH elevating substances but you must be careful when handling them.  They are calcium hydroxide (hydrated lime) and potassium hydroxide (old fashion potash lye.)

Most people will take action to buffer when their pH drops to below 6.5 and try not to buffer above about 7.0 and take a few days to do it since you don't want to raise or lower your pH much more than 0.2 per day since sudden pH shifts tend to be hard on plants, fish and bacteria.

Well, I was gonna blabla my  run -o- the mill answer until I read back a few pages...Holy crap! Are you really adding 4 spoonfuls of Potassium Carbonate (K2CO3) every couple of days, and STILL not getting a reading ABOVE 6.0? And you say that when you test your tap water it's pH 7.6 (I'm not even gonna ask if you let the tap water sit out over night before you test it...which would be a good idea, so's that you can get a more realistic reading)...Man, with with Poatassium Carbonate you should be able to get away with using about a 1/3 less (per dry weight basis) than with Potassium Bicarbonate (KHCO3) (which is what most people use...4 Tsp might not be much, but 16 or 24 or whatever you've added, might be...especially in a non-nitrifying just newly filled with system...filled with pH 7.6 tap water no less)...

I'm stumpified?...your not getting nitrites/nitrates, so there's no nitrification going on to lower the pH... you just started cycling (24 hours)  when you noticed the pH at 6.0 (or below)'ve been adding a pretty strong-ish bufferevery other day or's doing nothing...

WTF? Did you try lowering your pH with anything before you started cycling? Did your cat knock over the bottle of Muratic acid that sits on the shelf above the tank? Something very UN-run of the mill is going on...

It's prob not your test kit since your tap will read 7.6 right? and apparently you know how to use the kit...

Hey, tell me this...what happens when you add some of that K2CO3 to a 5 gallon bucket of tap water? Add an amount proportional to what you've been adding to the system.

Did you buy the K2CO3 from a store? Is it labelled? Or, did your neighbor's, friends' drunken Uncle who runs a meth lab give you a bag of pearly white powder and tell you he thinks it's Potassium Carbonate...?

Test your media pH with a jar of tap water and a handful of the hydroton you used...see what comes up?


I didn't let the tap water sit overnight. I will try that.  My mistake earlier too, it's potassium bicarbonate.

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