Aquaponics - On demand fish feeder

A while ago I tried to make a fish fed fish feeder design that would allow the fish to feed themselves.

I think It's made.

I say "think" because the fish have only triggered it twice in its first 12 hours of it being set up in their tank, and it's too early to tell if it works.

I bought a small 12 volt electric motor and gearbox, and connected it to an old drill bit from a hand cranked wood drill.

I cut a section of PVC pipe lengthways as a feed hopper, and filled it with feed.

The gearbox on the motor means the output shaft spins at only 36 revolutions per minute, and is quite powerful.

The next step was to find a switch that was very delicate to operate, so the fish could just lightly touch it to activate the motor.

I found a suitable lever switch, and glued on a plastic knife to extend the lever down into the water.






Now if the fish touch the lever, the motor engages, rotating the drill bit, forcing a small amount of feed along the PVC hopper into the fish tank.


I added a key, and a clip from my office as additional weight to set the trigger closer to being activated so the the fish need not hit the lever so hard.

It does actually seem to work, and the fish have set it off twice so far.

Only time will tell if it will really work as a feeder, or if every now and again, a fish just bumps into it and never associates the drop of food with the press of the lever.

[Note from the future - there is a LOT more to this project in later posts, including a new digital version where you can set the total amount of feed from a pinch to a bucket, and a stack of other features including a dawn reset so the fish can live on natural time rather than Greenwich imposed human time - there is also a video of the fish feeding themselves, and here is the results of a search on this blog for fish feeder for a stack more information]

Aquaponics - Inverter based electrical backup system

We get a lot of blackouts.

Fish hate blackouts.

I'm going to blackout proof my planned, larger, aquaponics system by building an electrical backup. I also need to build my planned, larger, aquaponics system.

Here's what I've done so far...

Attractive isn't it.

I happen to own a one hundred amp hour deep cycle battery. That's it in the bottom right corner of the picture.

I also own a multi-meter, a battery charger, a powerhead, and a bucket of water. 

As of today I also, also own a 200 watt inverter. It's a device that turns 12 volt battery power, into mains power. I had to buy it. A small inverter doesn't cost much and you can pick one up online, or in camping sections of department stores.

A power head is essentially a fish tank stirrer. It aids in supplying the water with oxygen, and will also create a bit of a whirlpool to concentrate fish waste solids into the center of the planned, larger, fish tank. This will allow the solids to be extracted from the fish tank, and moved to the planned grow bed where they belong. 

The powerhead is a critical component, because I'll be relying on it to supply oxygen to my fish in case of a power outage or pump failure. That's the powerhead in the blue bucket. It's basically just a small motor with a propeller on it. According to the box it came in, it moves 5000 litres of water per hour. The best part is, it moves all that water with only a 12 watt motor. My pump also moves about 5000 litres of water, but it has a 150 watt motor. 

The pump's main purpose in life is to supply the grow bed with nutrient rich water, but the bacteria will be fine for a couple of days if it fails. A system full of fish on the other hand, will start to suffer within an hour or so if the water isn't moved around.

I'll run the pump on a timer, so that it runs for around 10 minutes of every hour. I'll run the power head all the time.

The plan is to run the powerhead from the large battery, via the inverter, and to run a battery charger to keep the battery topped up at all times. Based on the tests I'm currently running, and on my rough calculations, in the event of a blackout, I estimate the battery should last approximately forever. 

So far I've been running the powerhead for 4 hours using the battery alone (ie without the charger), and the batteries capacity has actually increased. Which is odd. I'm guessing it has something to do with the day warming up, which might be changing the battery's abilities. 

This electricity stuff is really the kind of thing I should know something about. Perhaps I'll look into it.