Aquaponic Fish

**This post continues our series on the aquaponic system we set up in our apartment last year.**

Possibly the funnest choice one gets to make in setting up an aquaponic system is the one about fish.  What type of fish?  How many can I grow?  Are there freshwater sharks?  Could piranhas actually help dispose of unwanted house guests and pesky city squirrels?

For us, locating the right type of fish on a proper scale was one of the hardest tasks.  If you have a large system and don't mind paying $80+ for overnight shipping, have no worries.  You can probably get whatever you want without much trouble.  If you only want five (edible) fish like we did, be ready for lots of phone calls and incredulous responses.  In this post, we want to talk about the types of fish we considered, how we found the ones we wanted (kind of), and our experiences with them in our system.

We only had a 50 gallon tank, so we wanted something with a relatively small mature size.  We made an assumption, possibly incorrect, that fish with a large mature size would initially 'add frame' and then bulk out.  That ruled out large species like bass and catfish.  We knew we had limited time at our location, and so we wanted something that would grow to worthwhile-eating size in less than a year.  This ruled out slow-growing wild species like bluegill. We also knew that we didn't want to have fish that would be sensitive to high water temperatures or low-oxygen conditions like trout (an assumption that may also have been incorrect).  Finally, we wanted something that would be easy to fillet, with a simple bone structure, which ruled out goldfish, koi, and other carp species.  We also considered crustaceans like crayfish, but decided against it for some reason we can't remember now, and minnows for fishing bait. We probably would have done minnows since they're cheap and readily available (and apparently work well!), but weren't excited about the local wild fishing prospects where we would use them as bait, wherein it was hard to find unpolluted waters.  Katie said we couldn't turn them into sardines.  So in short, we narrowed the field to tilapia.

Bone structures that must be considered when filleting fish.  View is looking along backbone (black dot) of fish, blue lines represent bones other than the rib cage (pin bones, lateral line bones, or "floating intramuscular" bones.  Sources: Temagami Stewardship Council (three on the left), LSU Agriculture Center (carp), Pacu.

Even among tilapia, there are a number of choices.  We looked at a number of online sources, none local to us, which meant high shipping costs and a typical minimum order of ~25 fish.  Too large a scale for us.  We searched and searched local pet stores, and finally came up with one an hour away that didn't have tilapia in stock, but was willing to find some for us.  What they came up with (after considerable searching of their own, it seemed) was Tilapia Buttikoferi, which we were initially excited about.  Evidently, they thrive at lower pH than other tilapia species (closer to the range plants prefer), prefer somewhat cooler temperatures, and grow relatively fast, at least compared to other aquarium fish.  They also typically get aggressive when larger, but we figured it would be ok to start with them.

Comparison of Buttikoferi with other commonly grown aquaponic tilapia species.  Sources: Fishbase.org for Buttikoferi, Nile, Blue, and Mozambique; IJAB and SDSU for some pH data.

They arrived in what seemed to be good shape as 2" fingerlings, acclimated to the tank without much trouble, and initially even nibbled on food we gave them.  Unfortunately, it went downhill from there.  They were never active eaters, and didn't grow quickly.  They took advantage of coffee mugs we put in the tank for cover but were often inactive (although they normally swam to the back of the tank when we were around), and eventually all six died.  NH₃ and NO₂^- levels were consistently zero and the pH ranged between 6.5 and 7.2.  Temperature was steady at 75 °F.

The little fishies, fresh from the pet store.  All six looking relatively healthy.  Only two grew noticeably larger than this, and unfortunately, none made it to our table.  Cause of death: undetermined.

We haven't figured out why they didn't grow well and eventually expired.  Did they come with a disease we didn't know about and eventually all succumb to it?  Was the salinity of our water too low or too high?  Did we contract a disease in our water that we didn't know about?  Symptoms of the common fish diseases didn't match up with our fishes' behavior, as far as we could tell.  Where's that darn Sherlock when you need him?

One incident is worth commenting on.  When we had to be away for a weekend, we got an automatic fish feeder and set it up (the one on the left in the picture below).  It seemed to be working well, but when we came back from our weekend away, the feed canister had fallen into the tank, spilling most of the food, and three of the fish were dead. (Although when we tested for ammonia levels, they were < 0.25 ppm.)  Did the fish overeat on their sudden smorgasbord?  Probably not, since they weren't even excited about the pinches of food we were normally feeding them.  Was there a spike in ammonia to which they fell victim?  The mystery remains.  Later on, when we were going to be gone for another weekend, we set up a second automatic fish feeder  (on the right in the picture below), which just didn't work.  Fresh battery when we left, just didn't dispense food.  The second time there were no adverse effects on the fish, just disappointment in our feeder.

The two automatic fish feeders we tried, neither of which worked well for us.

So, despite our thorough fish species research and rock-solid fish-choosing logic, we didn't end up putting any fish on the table.  But still, we don't want to leave this post with a negative message!  So, what did we learn from this experience?  First, our plants grew fairly well on a pretty minimal nutrient load.  Basil, thyme, chives, and swiss chard were our most prolific producers, with about as much as we cared to eat.  Dandelion greens weren't far behind, and our green onion also did well.  And that was on the nutrient load from five fingerling fish.  Imagine how they would have done if the fish had grown at all!  Second, the pH was quite steady, even in a 50 gal tank, which is on the small end of aquaponic setups and rumored to be prone to unwieldy pH swings.  Part of our stability was likely because the fish stayed small (others seem to experience a consistent pH decrease if they don't correct it as the fish grow), but we'll call it a success nonetheless.  Third, our aquaponic system design was for the most part solid, and worked for more than a year (other than the fish not surviving).  We'll make a few changes in version 2.0, but the design should (we think) definitely get a passing grade.

We'll post updates when we get our new system up and running, so check back often!

Do you have any experience with buttikoferi in aquaponic systems?  Any thoughts on why our fish didn't make it?  Let us know in the comments section below!

Other posts in this series:
Review of Aquaponic Gardening by Sylvia Bernstein
Design of our aquaponic system
Construction of our aquaponic system
Preparation our aquaponic water