Electronics - Aquaponics - Demand feeder PVC mockup

I think I have a final design idea for my demand feeder. It's only a mockup, at the moment, ie: it's only the PVC parts without any electronics or bearings.

The more I learn about this electronics stuff, the more places within aquaponics I can see uses for it.

I'll do a proper one of my Build posts when I have everything in order, but this is where it's at right now.

The basic design is a 90mm pvc section to hold the electronics (seen at the back or top left).

This keeps the electronics away from the feed and any moisture in a grow house or that just might be splashed around by fish expressing joy at their new feeder.

The electronics section is coupled to a 90mm T-junction to integrate the hopper.

In this case I've used a soft drink bottle, but any sized hopper could be attached. Another option would be one of those office water cooler bottles. Clear so you can see how much feed remains.

Perhaps for ease of refill, the top of a bottle could be cut of to act as a funnel. This could be screwed into the cap allowing the user to simply upend a similar bottle full of food into the hopper funnel.

Finally, the feed is delivered via an PICAXE controlled electric motor, rotating a screw in a 55mm (I think) PVC inner pipe. This holds the front bearing (the rear bearing is the motor, and is housed within the electronics section.

I cut an outlet hole to actually deliver the feed to the fish. I set the hole at the bottom rather than just letting the feed flow out of an open end to avoid water dripping into the feed. This could turn it into a gluggy mess, and jam the system.

The final mockup looks like this.

It'll work.
























Not just Electronics - Aquaponics - Demand feeder PVC mockup -  120 Things in 20 years

Aquaponics - Restricting the feed intake to a system

This post relates to my ongoing electronics project Electronics - PICAXE fish feeder

The feed able to be dropped into the system is limited by the population of bacteria. They are in turn limited in population size by the amount of available real estate on the grow media, and to some extent other surfaces and even free floating within the water.

It's the bacteria that process the fish exhalations and excretions. As fish poop and breath, they add to the ammonia load within the system. The bacteria convert the ammonia to first nitrites, then nitrates. It's the nitrates that most plants enjoy, and the nitrates are not toxic to fish until they are very high.

Ammonia and nitrites one the other hand are very toxic to fish.

So we need to be careful not to overstock our systems with fish, but more importantly, we need to not over feed our systems.

And it really is the system we are feeding, not just the fish.

Generally in aquaponics, we talk about maximum fish stocking levels within a system, but it might be just as useful to talk about maximum feeding levels for a given amount of grow media.

In a small system like mine, I long ago gave up on the idea of eating fish every week. My feeding regimen isn't really about maximising fish growth. I have a set maximum amount of feed that I can add to the system without seeing ammonia and nitrites. When I feed my fish I have a little jar with a level marked on it. I fill the jar to that level each day, and don't ever feed them more than that. I feed them less that that, if the don't want to eat it due to temperature, or whatever fishy reasons fish have for not eating, but they cant ever have more because because the system cant ever have more.

Actually the system can have a bit more, but this way when I find caterpillars and worms and things I can add them at will.

Generally speaking it's also a good idea to run your system below it's maximum feed capacity, so that if something goes wrong, you have some margin for error.

If, for instance, a fish were to die and I didn't notice it for a few days, it would create a huge ammonia spike. That ammonia might take a few days for the system to process, and in my system, I'd get away with it, but if I ran my system closer to it's maximum feed input, an event like a fish death could be catastrophic.

It's ok to run your system close to the edge, but you have to be there all the time, and check it all the time.

I prefer being relaxed.



Not just Aquaponics - Restricting the feed intake to a system - 120 things in 20 years