Aquaponics - Carrot growth

My carrots are growing.

Which is nice.

They, or at least this one, looks like this.

Some stuff take a long time to grow.

I have very low levels of nitrate (plant num-nums) in my system due to having only two fish, and sleepy ones at that.

The water temperatures are sitting at around 10c, and the growhouse has similar air temperatures.

All that means my fish are almost dormant, and only eat a tiny amount every second day. No feed, and no activity mean no plant nutrient. I should have got some trout, (trout love the cold water) but I was waiting for some more silver perch, and also expected this grow house to keep temperatures up a bit higher. Unfortunately, the fish farm I normally get them from, had some kind of spawning fail, so I didn't get any.

In other news in the grow house, there is no new news. Everything is sleeping except lettuce.

I think I need to seal up my solar panel, and connect it to my fish tank heater. It's a 300 watt heater, which is quite powerful for a fish tank heater, but I suspect it won't do a lot in a thousand liters of water that's outside.

120 Things in 20 years needs to have bought a bigger and better grow house if it wanted decent aquaponics carrot growth.


  1. Solar heat is awesome. Just apply it directly.

    Use the solar panel to run a small pump that pumps water into a large flat shallow tray of water that is covered with a sheet of black plastic. Let it overflow back into your tank - the same flow process as your grow bed.

    The pump will run when it's sunny, so you should only be moving warm water into the tank during the day.

    Your next new thing? A solar water heater?

  2. I actually did some work on solar hot water as a thing...

    And it's possible to use a thermo-siphon to pump the water around passively...

    But the problem is going to be just how much fish tank I have. 1000 litres of water is a lot to heat, and I have the solar panel and heater just sitting there. If I buy enough clear plastic to collect enough heat, I may as well make it a grow house. I'm about to buy a stack of strawberry runners in the next week or so, and have been giving some thought to a grow house that's just deep enough to grow strawberries. That would mean a large surface area solar collector, but with the added advantage of strawberries.

    This reply is turning into a blog post :)

    I need to buy a MPPT solar charger first. I need to buy one for my epic river adventure anyway, but this 120 things thing is supposed to be revenue neutral so it will have to wait :)

    I guess I could just knock one of the fish on the head and sell it to myself at 3 Michelin star rated restaurant sushimi prices.

    That should cover it.

  3. Got any friends with a solar swimming pool heater you can examine? They are actually surprisingly small.

    Even diverting a little bit of water from the grow bed onto a heater panel the size of a door should give you some heat gain. Somehow you want it to only work during the day so you don't end up making a radiant water cooler (those work really well on clear nights - ten degrees below ambient!) on accident.

    You'd want to insulate the tank so you don't loose all your heat over night.

  4. This comment has been removed by the author.

  5. One of the issues is that you cant really insulate the fish tank when the water is going through large surface area grow beds (read "heat exchangers")at a turnover rate of 1000+LPH ie the entire fish tank is put through the grow beds every hour.

    When I had the clear plastic grow house, and only 200L of system, I was seeing much better heat gains as graphe[d] here...

    The overnight losses are not as important as getting that water above 16c for at least a little while each day as that makes the fish active and hungry.


Popular Posts