Backyard Aquaponics
A place to discuss aquaponics

About a year ago I purchased 20 goldfish that averaged 2 to 3 years in age. They are an average of 7 to 9 inches long at this time. They are in a 700 gallon tank. The tanks overflow is about 6.5’ high and runs into a waist high grow bed that is 4 feet wide and 20 feet long. The grow media is river rock about 3/4 inch in size. This system is large and not without its own troubles which I've been trying to address.

But the strangest observation was noticed today… I always have my 24’ long x 3’ wide sump (which is 2 feet in the ground) covered to keep the sun off the water. Half of it is covered with a metal cover while the other half is covered by floating rafts. I removed some of the metal covering this morning and noticed a 2” or 3” long gold fish in the sump! Where did that fish come from? The only fish I purchased (just over a year ago) were all at least 6” or larger. Even if the fish were reproducing it’s hard for me to believe an (uneaten) egg would have made it all the way through that 20’ gravel media and into the sump, hatched and then grew to that size in a year with nothing to eat but the roots of the plants in those rafts.

I’ve not moved all the rafts and metal covers to see if there were any more.
I’m sure it’s my lack of experience that has me stumped…

Very puzzling situation… any thoughts?

Depending how big the spawn was, that single goldfish was the one in a million. Not unheard of to have a spawn unknown and find some fish in the sump or swirl filter. To have one make it through the gravel grow bed is pretty miraculous. I would name that fish Lucky and let him pick lotterie numbers.

My system goes from FT, through a filter, into the sump that feeds the grow bed and it drains back into FT. I have found fish in my filter and sump before I redid my SLO to prevent that. Getting a 1 inch fish out of my filter took me hours.

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yep eggs / fry can end up anywhere



I had some perch fry escape recently they ended up growing for a few months in between the fish guard and the radial flow filter pipe , disconnected the ~1m long 50mm pipe section to do maintenance to find a handful of 30+ gram fishes gush out

Sorry for not coming back here immediately... But after posting this the other day I took the sump apart (all 24 feet of it) and found another 3 smaller dark fish.. Several of my large goldfish are actually very dark with no color at all so it doesn't surprise me there would be a few dark fry. So that's a total for fish I found eating roots from my floating rafts in the sump.

You would be surprised at how fish can go through a pump and come out okay. i have found little gold fish in my grow bed before and they would have to have gone through the pump to get there . There were none in the tank so I guess that the rest got eaten. Sometimes the first you know about tilapia having babys is that there are little ones in the grow bed.

I recently found two 6" tilapia in one of my sumps. In my case the fry traveled from the tank, through the RFF to the growbeds, then rode the siphon into the sump and survived for probably a year on roots, algae and detritus. I never expected them to get so BIG. I recently discovered them, and transferred them into a normal population.