Our experience with bullhead catfish in aquaponics

 baby catfish3

The most popular fish for aquaponics tend to be tilapia, blue catfish, and goldfish. Though it is my plan to transition to tilapia, up till now, we did not have a greenhouse designed to keep them warm enough through winter. I hope that will change with the new greenhouse we are planning to build. The big advantages of tilapia is that they eat almost anything, grow very quickly, are very hardy if the water is warm enough, taste very good, and reproduce easily in captivity. The big disadvantage with tilapia is that they die when the water temperature dips below 60 degrees and really need to be in the seventies at least, to be healthy. Without a well designed system, they cost a fortune to keep alive over winter and are not really practical outdoors in a temperate climate.

I attempted to raise blue catfish the first time I tried aquaponics. Just as they were ready for harvest, my family and I went away for two days mid summer. And mid afternoon (during the heat of the day) on both of those days, the power company decided to work on nearby power lines and turned off the power. When we got back, the catfish were ready for the compost pile. It was extremely disappointing, to say the least.  The big advantages with blue catfish is that are readily available and taste good. And they are hardier than some other common cold water fish (bass, perch, etc). The big disadvantages with blue catfish is that they are not as hardy as tilapia and cannot reproduce in captivity. They are primarily carnivorous, and that limits what can be fed to them if you are not feeding commercial pelleted fish food.

Goldfish, are well…goldfish. They may provide the waste necessary to support an aquaponics system and they are extremely hardy (a good beginner fish) but they are not normally eaten by people. And half the fun of aquaponics is raising fish that can be eaten.

There is another alternative very rarely considered by aquaponics enthusiasts because it is considered a “trash fish” in this country. And it is bullhead catfish. Bullheads do not get as big as blue catfish. That is one reason they are unpopular. And they can taste mucky if they are raised in mucky water. But they have some advantages that should make them worth considering for the purpose of aquaponics.

  • They can taste very good if raised in clean water (better harvested when the water is cold, though, for firmer flesh).
  • They are common in the US and can be easily caught from the wild.
  • They are extremely hardy, as hardy as goldfish, and hardier than even tilapia.
  • They grow quickly the first couple of years then slow down. They should be harvested at this point anyway, because they become more aggressive towards one another in their third year of life.
  • They can reproduce in captivity.
  • They are omnivores and eat almost anything (like tilapia).

catfish eggs

Bullhead catfish eggs.

baby catfish 4

Baby bullhead catfish fry.

What I have learned about bullhead catfish:

  • They are most likely to breed at two years old. They become aggressive at this age and need to be separated, a few per container. Any two year old fish not intended for breeding should be harvested at this time. They start killing each other otherwise as they become more territorial.
  • They like to lay their eggs in sand or muck on the bottom. They did fine separated into horse troughs with some sand on the bottom, sunken plastic pots for shelter and aerator stones. We did not have an aquaponics system set up for these tanks and I would use a bucket to scoop out water occasionally for the garden and refill as necessary with water from the well. With only a few fish per container, water quality wasn’t a big issue.
  • If there is a water pump, it would require a fine screen so that the baby fish would not be sucked up. They alternate between feeding on the bottom of the tank and surfacing to feed for algae on the sides of the tank.
  • Bullhead do better in shallower tanks verses tall ones. They can handle periods of no aeration or water purification as long as the water is not too deep and they are not too heavily stocked. They are a very practical choice for a solar system not using a battery for overnight pumping.

baby catfish5

Overall, we were very pleased with our experience of using bullhead catfish. I am excited about the prospect of raising tilapia. But for cold water aquaponics, where sustainability  is important (not needing to regularly purchase new fish). bullheads proved to be a very good choice.

Earth tubes for geothermal green house heating and cooling

lines of earthtubes


My husband rented a 3′ trencher for laying down electrical conduit and a water-line for another construction project. But once he finished that, I asked him to dig trenches for me to lay down earth tubes for geothermal cooling in my next greenhouse project.



The trencher dug trenches close to 3′ deep and 6″ wide.


earthtube in trench


I then laid down perforated 4″ corrugated pipe. The perforations will allow water, which will condense out of the air as it is cooled, to seep out into the soil.


earthtube with gravel

I ended up putting two lines of pipes in the trenches, one to cool the greenhouse, and the other to provide geothermal cooling to a cob addition I want to add to the house. I then covered the pipes with pea gravel which has a high thermal density (allowing good heat transfer) as well as drainage for the moisture that will seep from the pipes. I then finished covering with sand.


earth tube intake


These drain pipes can be fitted with convenient attachments to keep animals out of the pipes and provide a nice finish to the air intake/outtake vents.

Geothermal cooling using earthtubes can employ fans and require electricity. But that isn’t necessary as long as hot air is able to escape the greenhouse, pulling in cool air through the vents.

This video describes a recirculating system requiring large fans.

In the system I am building, cooler air will enter the tubes from outside the greenhouse, under the raised pier and beam foundation of our house. This will be a significantly cooler location than anywhere outside exposed to the heating of the sun. It will then pass 30′ under ground through 9 4″ tubes, into the greenhouse. As air is vented from the greenhouse, whether by solar powered fans, solar chimneys, or natural ventilation at the roof-line, ground-cool air will be pulled in as long as any other openings are sealed.

The air coming into the greenhouse through these tubes will be dehumidified as well as cooled. As it warms, it will readily pick up moisture from the aquaponic beds and have an additional evaporative cooling effect. It will rise and be vented out, pulling more cooled air in behind it.

I could use this method for greenhouse heating in winter. But because my goal is to heat the greenhouse enough to keep tilapia alive year round, I need more heat than the ground can provide at our latitude (it is adequate to prevent freezes, but not adequate enough to keep tilapia happy). I also did not want to build a recirculatory system dependent on fans at this time. So I plan to use hot compost for winter heating instead, which also can incorporate earthtubes if I want..

An article on a partially excavated greenhouse in Nebraska also using earth tubes for winter-time heating.

Another good article on earth tubes.

Non-electric micro greenhouse heater

greenhouse peppers

My peppers have recovered beautifully from the last 20 degree freeze in their new micro-greenhouse. Now I am preparing to keep them alive as winter progresses with likely much deeper freezes.

new heater pic 1

I kept my peppers alive a couple of weeks ago during the 20 freezes by using a heat lamp. But it is my preference to find off-grid solutions that are also inexpensive. I have used kerosene lamps before for this purpose but they tend to deposit soot on the plastic which is a problem to clean off, and kerosene is expensive. This year I am going to try these home made flower pot heaters. They should provide comparable heat to a kerosene lamp (at least the larger size I am making) but should be less expensive to operate and the soot should remain inside the pot.

new heater pic

There are several problems with the standard directions for these pots. One is the tea light candles most frequently recommended for this. Their burn time is just not long enough to get through the night. I don’t know about you, but I really don’t want to go out on a cold, cold night to switch them out with new ones. So I wanted to be able to use much larger, longer burning candles that also don’t cost a fortune. My solution is to use home-made, multi-wick candles using shortening or lard or other rendered fat from the homestead as a fuel (will make another post specifically on that). But to use this, I needed a deeper base that can hold them safely under the pots.

This leads into problem number 2 most commonly associated with this. Some use bread pans which are deeper but unstable. Another person screwed on the base which looked really nice, but would require more time and effort to screw off to put in new candles, especially if you are using something larger than the standard tea lights recommended for this. And his base was way too shallow for anything bigger than tea lights. I solved this problem by finding a clay square shaped pot that the larger pot (10″ can comfortably rest on) and the smaller 8″ pot can snugly fit inside, making a very stable and secure fit. The corners provide opening for oxygen to feed the candles so that I do not have to worry about any spacers. And the base is heavy enough to not be tippy when the heavy pots are fitted on top.

 lifting pot from base

I used a 6″ carriage bolt to hold the two pots together. It also allowed me to create a nice little handle so that I can easily lift the pots from the base.

Materials I used for creating my pot heaters

1 10″ clay pot

1 8″ clay pot

1 9″x4″ square clay pot for base

1 6″x1/2″ carriage bolt

(could be wider, the holes in these pots are closer to 3/4″ but this is what I had)

At least 2 2″x1/2″ washers (larger holes if you use wider bolts)

8 1″ (or 2″) x 1/2″ washers (again, should be sized to fit the bolt used)

9 1/2″ nuts (or sized to fit bolt used)

I first screw on a nut to the carriage bolt, but not all the way to leave enough to easily grab. I then slide on a 2 inch washer and then 10″ pot.

pot handle

Inside the pot I slid in a 2″ washer and then screw in tightly another nut.

pot washer nut

I then slide in another washer before sliding on the 8″ pot.

I  two pots together

I then alternate washers and nuts to fill the remaining length of bolt. It is my understanding that the purpose of this is to provide more thermal mass and store more heat. Not all pot heater directions, however, include this and a shorter bolt and fewer nuts and washers could be used.

I do not have grandiose expectations with this heater. It certainly is not a high btu device. But it is my hope that it is comparable to a kerosene lamp and will be enough to keep my peppers from freezing in their very small greenhouse. If we are expecting very low teens or single digit lows, I will probably put blankets over the greenhouses. But after my experience with the last freeze, I know a heat source is necessary. The black water barrels should help. But it is my hope that this simple and inexpensive device should provide an extra edge. We will see…

Putting up greenhouses within the shade house

shade house gate


We screwed 2″x3″ boards to support the center of a transparent greenhouse tarp to the center of each section of the shade house. My plan is to leave these tarps permanently screwed in, but to roll up the sides during the warm season and tie the rolls to the center boards supporting the tarp on the ceiling. The sides of the tarp are supported by electrical conduit, forming an arch. The frame of the shade house provides structure to support and put tension on these conduit pipes that it isn’t necessary to attach them to the sides. I just shoved the ends into the soil next to the framed sides of each section, and tied the center joint (required two pipes connected for each support) to the center board that is holding the center of the tarp to the ceiling. The beauty of this method is that the tarp is not damaged with additional holes, and the shade house frame and pvc provides plenty of support and protection from high winds. The shade cloth is still in place, and was reinforced enough last year to be able to handle the small amounts of snow and ice we typically receive. The shade cloth will keep snow and ice off the tarp, protecting the greenhouse.


I attached an old tarp on the back side (north) of the shade house.


And I hung a clear tarp on the south side, to enclose the greenhouse and allow entry.

These greenhouses will not be enough to protect my peppers and more sensitive warm season plants. But they will help heat the garden during the day and retain some heat at night. I am planning to add black water barrels, Hot compost grow beds, mini-greenhouses inside the big greenhouse with thermal mass, and other strategies to keep my more temperature sensitive plants alive and well through winter. I am very pleased with how this simple and relatively inexpensive addition dramatically increases the versatility and value of the shade house. The shade house has by far, proven to be the best and most efficient garden investment I have made in our extreme climate.

Here is a link for a page describing how to build hot bed cold frames:


Raised bed micro-greenhouse


We had our first freeze of the season last week where we had several days of sub-freezing temperatures dipping down to 20. I worked hard to keep some of my peppers and tomatoes alive by using heat lamps and covering them with standard tarps. Peppers and tomatoes are perennial if they are protected from frost and freezing temperatures. And I have learned through experience, that if I am able to keep them alive over winter, they start to produce much earlier, and far more heavily in the spring  than new transplants. And because the period of time between the last frost and 100 degree days of summer is relatively short, it is important to get as much production as early as possible in the spring. Though we have a very long season of frost free days, we actually have only two very short prime growing seasons, in the spring and fall. Only the most heat loving plants continue to produce in summer (winter squash, sweet potatoes and southern peas).


I ordered this from A1tarps.com

I have been needing to order these transparent tarps, but for financial reasons, I had to wait. I finally received them yesterday. Now that I have the tarps, I am putting together a more practical and sustainable (and hopefully non-electric) strategy to keep these more vulnerable plants alive during our hardest freezes.


I first placed two black barrels I purchased at a local feed store for $20 each, on each end of the bed. I then filled them with water and closed the lids. These barrels will absorb heat during the day and radiate it back at night, moderating the temperature inside the greenhouse. They also should help to prevent overheating during hotter days.


clip 3

My hoops for the garden bed uses 1/2 inch electrical conduit (cheaper and includes UV protection, a quality standard pvc does not have). For the hoop house clips, I cut 3/4 inch conduit.


To make clips, I first make two cuts down the length of the tube using the chop saw. I lower the blade, cut through the plastic, but not too deep, then slowly pull the pipe towards myself so that the saw cuts to the end. I then make a second cut doing the same thing. Because the tarp is heavy-weight, it is better to have the cuts further apart so that the clip is not too snug and wont tear the plastic when putting on or taking off.

cut clip 2

I then make two cuts, cutting two clips from the initial cuts down the pipe.

cut clip 1


In the event this is not adequate to protect the peppers when it gets really cold. I have a couple more ideas to add. One is to put the peppers in Wall-O-Waters.


Another option I will also be using during the coldest nights is this extra large  clay pot heater. It should be able to do what a kerosene lamp can in heat output, but without the soot and for far less cost in fuel. And I can use home-made candles made from rendered fat from the homestead.

new heater pic 1