Backyard Aquaponics
A place to discuss aquaponics

thanks Bcasey

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Good morning

I barely have time to write this morning as I made a mistake and drank a half of a cup of coffee yesterday after lunch and was up half the night.

Below is the description of the ratio between grow bed media and trout stocking capacity. This showed us that we need lots of media for the quantity of fish we want in our large pond. The next issue was making the sump tank large enough to handle all the water moving through the grow beds. Nell worked up the maths: We need actual square feet of submersed media and volume of water which we’re calling transient water. This transient water is what would spill back into the sump tank via gravity if all the pumps stopped. I had the opportunity to make the sump tank either 6 foot long or 7 if we needed the extra volume.

This isn’t high order math, nevertheless it is complicated. At issue is cubic feet of media in the first two grow beds I’ll build in the next weeks. Grow bed media cubic footage is related to fish stocking in this formula: “Now let’s assume you are stocking Trout, which require 25L+ of wet gravel per fish to safely achieve plate size.” Of course complicating things more is half of our volumes are in liters and the rest in Cubic feet. For example the clay media is 50 liters per bag and the lava rock is .5 Cubic Feet.

Transient water is the water from the pond moving through two drum filters and 5 grow beds into the sump tank and back into the pond. The sump must be large enough to handle the volume of water moving through the 2 drum filters and the grow beds. Calculations can be available next news letter. Results of the calculations for Volume of water are:

5 Grow Beds=100 gal water 2 Drum Filters= 45 gal water Total Transient Water = 145 gallons of water. Sump Tank Capacity is 210 gallons of water so we are in great shape there.

1 Trout needs 1 cubic foot of grow bed(?) with 60 % media and 40% water. Total Volume of grow beds is 45 cubic feet = 45 Trout. The question mark was added because we need to verify our Trout to cubic feet ratio. We will verify everything again of course before we start adding plants and fish. But we needed a basis for beginning.

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Yours truly,

Brian and Nell Rodgers

Brian,

I see your transient water figure for your 5 GBs. Must I assume that you have decided to go F&D instead of CF? Seeing that number seems a little on the high side for CF.

yes decided to get the highest cubic feet of media to allow us to get a good stocking load (trout) for this big FT, ASAP. F&D seems like the best filtration for that. I still want DWC tanks, but they'll need to wait, Spring has sprung and my wife is getting a little frustrated with the expense just to get the pond up and running. I lied saying we're near the hump, and it would be far cheaper soon with less maintenance because of all the forethought

Running either CF or F&D doesn't change the amount of media at all. It is just removing the bell from the bell siphon, and using the standpipe only. It also allows for more water in your system for added stability. Also with CF more of your media stays "wet" more of the time.

oh okay, any other benies to CF?s I hadn't got around to learning about bell siphons yet so . . .

I'm thrilled my wife is taking an interest in the AP. She is working up the volume for the highly irregular shape pond/FT. She has the top three feet figured as it is the closest to square walls: One prism and one cube coming out to 1380 gallons, just for the top!




She is also asking good questions: If the media takes up 60% of the cubic feet of volume, do we also need to remove up to three inches of bed water volume since the media does not come to the top of our 12 inch deep media beds and is below the surface of the media? In our first calculations meant to size the sump tank volume we calculated 40% water minus three inches below the sides of the 12 inch deep media beds. Or, is trhe 40/60 ratio of water to media already account for the water being below the media and below the walls?

With CF you have a constant water level in the sump. This lets you -

- have a smaller sump - on the other hand some people feel that the water fluctuations with the siphons oxygenate the grow beds better and reduce the buildup of solids. I've been using CF for years and it works. You'll have a big enough sump you can run either way and that flexibility is a good thing as well although I don't miss using siphons.

- makes it easier to put an auto top up valve in the sump because the fluctuations are caused by evaporation. This is handy when you want to take a vacation.

- If you don't shrink the sump then it gives you more water in the system and this gives you a bit more system stability for things like temperature, pH... Probably not a big deal with a system the size of yours though.

In support of the siphon (or timed flood and drain), it makes sure that all of the media in the beds is used. If all the water is dumped, and refilled, it makes sure every part of the beds are getting fresh water, I'd imagine constant flood creates channels, so paths of least resistance through the media, so it's not working as effectively at using the media.

Plus, I have both F&D, and CF in my system, and the F&D still outperforms the CF. Quite obviously too.

Float valves still work just fine though, just put them slightly lower in the sump than you would in the CF system.

Fair enough Colum

Interesting how peoples systems differ. The BYAP trials thread showed that at low stocking densities it really didn't matter which of the methods was used. That's the way I've been running and it works great for me. Either way it's best not to let large areas become anaerobic because of solids accumulation.

I used to be concerned about the nutrients on the side of the bed away from the water inlet but pretty much everything I've tried grows there and some plants grow better there (Parsley in particular) . As far as the dissolved nutrients, I think it's kind of like putting purple dye in a stream of water, yes it flows downstream but it also diffuses outward and some is deflected by the rocks at the same time. Distribution piping cures the channeling question but doesn't seem really necessary



Sounds reasonable. I think there are situations where some valves wouldn't work at all and others wouldn't work very well, like tall narrow sump tanks or tanks where you've maxed out the volume because of the number of grow beds. It would also be more likely for water to seep into the float as well, since it's connection would be underwater much of the time.

One other thing I didn't mention - you can add a CF bed to either type of system without enlarging the sump. This might come in handy for you if you want to expand the system later.

Sounds reasonable. I think there are situations where some valves wouldn't work at all and others wouldn't work very well, like tall narrow sump tanks or tanks where you've maxed out the volume because of the number of grow beds. It would also be more likely for water to seep into the float as well, since it's connection would be underwater much of the time.

One other thing I didn't mention - you can add a CF bed to either type of system without enlarging the sump. This might come in handy for you if you want to expand the system later.[/quote]



I would place the Float valve at the top of the sump and have a long arm on the float that can be bent to adjust the water level required like farmers here in Australia use in their stock troughs 25 years ago.

That way you don't have a hole half way down your sump and the valve mechanism is above the water level and it's only the float that is under water.

No mini float valves for you . That would work Joblow.

I stand by my original statement. You don't have to futz with figuring out where in the tank the ball valve float should be. With the siphons the level's always changing.

oh crap, I forgot about the float valve entirely. I should have plumbed one before this last batch of rockwork, grrr

I kind of thought of those issues when I imagined constant flood media beds. What came to my mind was keeping them clean or seasonal cleanings, seems like a rpita

having zero experience here makes my credibility pretty bad, but I am totally willing to experiment. As I'm all in with my system, and my wife basically calling me, (sorry, I don't play cards and should use another analogy) I feel I need to do the simplest setup and get the dang plants in. I still haven't build\t the grow bed rack, still haven't figured out how to install plumbing into wooden sided plastic sheet lined grow beds, nor how exactly how the bell siphon works. Colum, I want to take another tour of your steel grow bed design and construction technique, as yours is the closest to what I'm doing. I can't remember if I posted one of my napkin sketches of my planned steel work.