Handling Flooding Rains

[Paula]

I'm in the process of setting up my first system here in south Florida and am seeing a problem already. This time of year we get rains that regularly (often on a daily basis) overflow my pool and flood the surrounding area with 2+ inches of water before they're done (all within a very short period of time.) I plan to partially cover my fish tank (150 gal) but I see a big problem with the grow beds over-filling everything and, thus, the FT. Am I anticipating a problem that really won't be? Or is there something I can do in this initial setup phase that will take care of this?

I hadn't planned on using a sump tank, but is this something I may have to do (or take the chances of fish flowing from the FT into my pool?!) My initial setup is(was) going to look like this: 150 gallon FT with 2 (50 gal) grow beds (I'm planning to either add a 3rd 50gal GB later or NFTs or a DWC). I'd planned a timed F&D with the pump in the FT going directly to the GBs and then back.

Any advice would be very welcome! Thank you. =Paula

[George]

My system is outdoors and rain simply serves to top up the tank.  I'm sure some nutrients are lost when the tank overflows but I'm not concerned about it.  Be sure your tank is above ground far enough that surface water doesn't flow into it, or sump, depending on your design.  My tank is mostly in the ground with 6-8 inches above ground.  Good luck.

[Harold Sukhbir]

Hi Paula,

I had a system set up similar to the one you're proposing. I had an overflow line about 2" from the top of the FT connected to a 55 gal barrel on its side(lower than the height of the FT) which acted as an overflow reservoir or sump. The barrel had a small pump which i used to top up the FT when times were dry. Both i and the fish have worked very hard to build these nutrients so that this way i saved as much nutrient as possible.  I positioned a second line 3/4" above this one in the FT acting as an overflow line. Both lines were fitted with a cap with tiny holes drilled into them. When the barrel fills up to capacity, only then would the FT overflow through the second pipe. If you have the means you can make the reservoir larger than mine was, so that you save all the overflowing water and keep it for the hot days that will come. A small bubbler(aquarium air pump) will ensure enough O2 keeps the overflow solution aerobic until you need it!

[Paula]

Thank you for your responses!

So...hmm...first off, the FT will be completely above ground, so I won't have to worry about surface water contaminating the system. However, fishy water getting into the swimming pool might have to be considered. (Okay, I'm not all that worried about this, but my husband and kids find the idea a little off-putting. I wonder why?) George, do you get these heavy rains as well? Getting 4+ inches in half an hour isn't that unusual, but if it just doesn't make that much of a difference, that's good to know.

Otoh, I hadn't considered simply setting up a run off tank. That might be pretty easy to add without making big changes to my current design. I do have several sub-irrigation planters going that I could easily make use of this water (if it gets overfilled, too.) Good idea!

[George]

In recent years, it's been rather dry here in N. Fl.  However, during June it rained about 20 inches (tropical storm) but not a lot since then, just enough really.  Since your tank will be above ground, you can easily plumb an overflow to run wherever you want it, possibly to a tree or something that could use the fertilizer.  My tank has overflowed only a few times during the 8 months or so it has been running.  It takes about one inch of rain to add one foot of water to my tank.  Lately the timing has been such that just as my tank falls to the top up point, it rains enough for a fill up.

[George]

There wouldn't be anything fishy about it but it might be somewhat nutrient rich, possibly causing a bit of plankton bloom - rain alone probably triggers that already.  The fish solids will be either at the bottom of the tank or in the media beds and will not run off during an overflow. 

Paula said:

However, fishy water getting into the swimming pool might have to be considered.

[Paula]

"The fish solids will be either at the bottom of the tank or in the media beds and will not run off during an overflow. "

That's good to know. I'll pass that info along at an appropriate time. 

I'm thinking I'll set up a run off tank and then use that for the rest of my garden or for refilling the system if it gets low. When it rains here like it does, the whole yard is pretty much a soggy mess.

Thanks again!

[TCLynx]

So long as you install a big enough overflow a few inches below the lip of the fish tank (and put a grate or screen over it, you shouldn't need to worry about fish washing out of the fish tank and into your swimming pool.)

The dilution of nutrients from daily extreme rain events might be an issue if you don't have very many fish and the rains continue daily long term.

A roof of some sort over the system could help and collecting the rain from the roof have on hand for top ups instead of using well or city water might be handy.  The fish tank can easily be covered and protected from rain but the grow beds would probably need a clear cover of sorts.

[Paula]

Thank you, TCLynx, for you input! Holes for overflow with grates. Got it! I'll probably need a couple at least. I guess I'll worry about the nutrient issues later on. Probably by the time I get the system up, I'll only have a month left of these heavy rains to worry about. Maybe by next summer the system will have been going long enough to not have to worry so much?

I'll have to see about some kind of cover for the GBs. My plan is to place the FT inside my pool area as there are many osprey and other assorted fish loving birds right in my neighborhood and often my yard. Even a pair of bald eagles (though I don't know if they'd go after fish in plastic ponds...) But I'm going to have the GBs outside of it. Rigging up some kind of cover will take some thought. Along with the hard rains we get lots of wind. Hmm...