Water heating update

Just a quick note to record the apparent success of my little heater for the fish water.
My last post detailed the construction of a very simple black polytube heater which seems to be doing the job!!!
After about 2 weeks of operation it looks like the daily addition of just 1 degree of extra heat from the unit has raised the daily minimum temps , in the fish tank, from a low of 6 or 7 to a low of almost 10 degrees now. Still not warm but I think I am finally winning.
This new heat is a bit late for all those poor little catfish but next winter things will be better!!
Yesterday the minimum was 9.6 degrees- but it was a very cold day- it actually snowed quite heavily for about 15 minutes!! At the time Di and I were working in the chook yard making a new house for the new silkies- but that is another story.

I have also added a timer switch to the big pump setup so that the water is only pumped to the growbeds between 8AM and 8PM. The reasoning here is that the growbeds cool down during the night and so will tend to chill the water passing through them.

I have also got the differential switch working and so I don't have to go down twice a day to connect the 12V pump running the water to the heater.
Needless to say all is not quite a bed of roses- the pump draws more power than one 20watt solar panel can comfortably supply and so I have added a second 20watt PV panel.
This problem should be fixed soon as I have a mini maximizer kit which I will build and install when we get back from our little holiday to Hong Kong. This kit adjusts the voltage from the panels to enable a much more efficient conversion of the power from the panel to the load.

Winter Woes

A totally gratuitous image to start this post- this was the view I had when I wandered over to the big shed this morning to check on the fish. The local kangaroos are almost tame- certainly not much bothered by us- or by the dogs provided we keep the dogs close to us.



The period since my last post have been a series of learning experiences- most of them not good.
As we are still in winter the temperatures are still low- both outside, in the shed, and much more significantly, in the fish tank water.
My reasoning for putting the fish tank in an insulated hole in the ground were based on the assumption that the water temperature would be more stable. This has been the case. I also thought that the lowest water temps would be somewhat higher than I have actually measured.
I have been recording all sorts of details including maximum and minimum temperatures in both the shed and the fish tank water.
To date the lowest room temp over the last two months or so has been just above freezing. Night time temps have often been below 3 degrees C in the shed. Daytime temps have been as high as 17 or 18 degrees. And the daily fluctuation has been as much as 15 degrees or so.
At the same time the lowest water temps have been in the 6 to 7 degrees C range with a daily variation of less than 2 degrees. So as far as variation is concerned the buried tank works.
However the stability is a bit of a two edged sword- the tank doesn't heat up much without help from me.
At the start of this adventure I chose Tandanus tandanus and Bidyanus bidyanus species as the literature suggests that they will both survive temperatures as low as 2 degrees C. Perhaps well fed adults will but little fry clearly will not.

I think I have lost ALL of the Tandanus and perhaps another 10 or 15 of the Silver perch.

The highest numbers of deaths almost always follow the coldest days.

On a positive note the fish are still eating some Daphnia which fortunately is in good supply - they refuse all other non live food. They even reject chopped earthworms which were a favorite in warmer times.

I have even contemplated growing trout next time- however that probably won't happen for another reason- the lower temps are not only bad for the fish but also for the bacteria which are responsible for changing the fish waste into plant food.

The growth of the current plants has almost stopped. I doubt if this is due to a lack of nutrients as much as simply a medium which is too cold. I reckon that in a dirt garden the soil can soak up a bit of heat from the sun and this help the plants. My plants are constantly bathed in coldish water. Perhaps I need to do some more experiments in this area.
Having said the above- all is not doom and gloom- the peas are sort of growing. And the tat soi has a bunch of pretty flowers. The tomatoes have all been removed.

And so I tried to adapt an old hot water solar panel heater to heat the water. As the solar panel has copper pipes and connections and copper is known to be toxic to fish I decided to make a heat exchange unit to transfer heat to the fish tank water without allowing the water heated in the solar panel to come into direct contact with the water in the fish tank. As the water in the heater panel would be subject to freezing I also used a glycol solution in the system. Glycol is also toxic to fish but I reasoned that the circulating water would not come in contact with the fish water so this would be OK. I made a big loop of plastic pipe to immerse in the fish tank and tried to pump the antifreeze solution around the system. Short answer - it didn't work- too much trouble getting the air out of the system etc. And the heat transfer ability of the plastic pipe is terrible. (Can't use copper for toxicity problem mentioned above, couldn't find aluminium pipe and stainless steel tube is VERY expensive).
So I have now made a much simpler heater for the water.
Basically it is 30 meters of 19mm polypipe inside the box that had held the first solar hot water heater panel. The water is simply pumped out of the fish tank through this polypipe and back into the fish tank. Crude measurements of water temp suggest that on a good sunny day, even at this time of year, I am getting a 1 degree increase in water temp during this pass through the unit. The pump I am using is a 12volt bilge pump rated at 350 litres per hour. The power for the pump is a 20Watt solar panel , a Solarex regulator and a couple of 20Ah sealed lead acid batteries. I am now trying to fix the differential heat switch which I am using in an effort to automate the process of pump on and off switching.
My current thinking is that I might be able to keep this heater going in the summer to get temperatures which should cause explosive fish growth. And perhaps even prevent the lows of this winter by "loading" up the tank and it's surrounds during the summer. Time will tell if this logic is sound or not.

To add to the problems I am having I have discovered, in the last couple of days, that the float switch which turns the big pump on and off has stopped working properly. Actually it is worse than that - it works intermittently. With a bit of luck a little adjustment to the weights and levels of the cables will fix this problem.

Cold weather

It is now officially winter where I live and it certainly feels like it. We have had a few frosts and most of the plants in the dirt garden are looking much the worst for it.
The tomatoes in the growbeds are still alive and there is still some fruit ripening on the vines. They look pretty sad as plants and I think this is probably due to some mineral deficiencies which I am attempting to remedy with blue metal crusher dust. I am told that basalt dust contains all sorts of mineral which will slowly become available to the plants. To this end I have mixed about 8 or 9 cupfulls into each growbed. Too late for these tomatoes but perhaps of use to the next crops.
Di has put in another crop of peas and they seem to be doing quite well.
This is despite overnight temps in the shed dropping to as low as 4 degrees C.
The water in the fish tank is now around the 10 degrees C mark and the fish are not eating much.

The fish are refusing everything except daphnia at the moment.
Fortunately I have found a source for good quantities of this and I collect a couple of litres of daphnia every week or so. I then put this into the spare water trough I have outside the shed and scoop out a couple of tablespoonsful daily or at least every couple of days. As it is alive this doesn't cause any problem in the fishtank if not eaten straight away. The picture is one I found on the net and looks just right. The dark "balls" inside the daphnia are eggs or the equivalent. These little critters are only a couple of millimeters long so are really just a viable food for the fish while they are at their current size of between 50 and 100mm.
On that note I have had the fish for almost 8 months and I must say I am somewhat disappointed in their growth rate. It looks like we will not be eating fish until next Autumn!! If then!!
As they are still so small it is simply amazing how much plant growth we have had. I can only assume that when the fish are almost at the harvest size that we will have riotous growth in the growbeds and will probably have to plant and harvest like crazy.


The 3rd picture shows the second
plantings of peas .
Peas were quite successful the first time around. As it is winter I expect this planting to be a bit slower to grow than last time but we will see.
Nothing quite like chomping on fresh peas straight from the bushes while doing fishkeeping chores. Enough still make it to the kitchen for stirfrys and the like.



The final picture in this post shows
some Tat soi which we are letting go to seed as Di couldn't find new seed for next time. This is an experiment and I don't know how succesful it will be but it is worth a try. And the flowers are quite pretty.
We let some coriander go to seed earlier and a few little plants have popped up in one of the other grow beds.

Insulating the growbeds

Today is Anzac day and that is traditionally the start of winter in this area.
I have been concerned for some time about how the fish will fare during the winter as it gets quite cold here in downtown Burra Creek. (Actually there is no town of Burra Creek- it is almost all ex farming land - never great farming land and now mostly hobby farms).
Already the nighttime temps are dropping below freezing outside and we have had cold enough weather to kill off the tomato plants which were growing in the dirt garden.

I had always intended to insulate the grow beds as they are above ground in the big shed and as the air temperature there is now dropping to as low as 6 or 7 degrees Celcius it is clear that the water temperatures will eventually drop as well. Current water minimums are in the 13 to 14 degree range so the tank insulation is clearly doing what it is supposed to do.

I had intended to wrap the growbeds with a product called Aircell which is a lot like heavy duty bubble wrap with a layer of heavy aluminium backed sisalation like material bonded to the bubbles. However I was quoted over $300 for a single roll which is 10 metres long by 1300mm wide. It would have been enough to wrap all the growbeds but I decided that was too much money. Instead I bought a similar sized roll of sisalation backed fibreglass batting for about $120. This was split into 3 rolls about 400mm wide and then wrapped around each growbed.
The reflective layer is fairly fragile so I then wrapped the beds with the Sisalation I took off the roof when the steel was replaced with polycarbonate.
This also had the benefit of covering over the fibreglass. This should protect the fibreglass from damage and also protect me from the batts which can cause a lot of itching.
We folded the extra Sisalation over the top lip of the growbeds . It is held to the top by a length of split 13mm poly pipe which should keep it all neat. Attaching the poly pipe was not a fun job but if it keeps the whole lot together it will have been worth the effort.

It will be very interesting to see if this part of my plan works as there will still be some heat loss from the tops of the growbeds. The next phase of the construction is the creating of a heating system for the water.

These 2 pictures were taken today. Sharp eyed viewers will notice the beans have gone from the closest growbed during the construction. Peas are the next crop to go in under the wire supports.
We have also pruned a fair bit of the tomato leaves from the plants which are still going well and with a bit of luck they will continue to produce fruit for some time yet.

Plant growth update

10ft tall tomatoes!!
Well perhaps not quite 10ft but they are much taller than I am even when I am standing on the gravel in the growbeds. In fact some seem to be trying to escape out the window at the top ridge of the shed.
The first picture shows the tomatoes about 6 weeks ago and the second , more recent picture, shows much bushier growth with runners almost to the roof! We have eaten a fair few of the fruit but there are now a bit hard to find in amongst the foliage. I plan to do a fair bit of leaf pruning fairly soon. Early fears that the flowers would not be pollinated don't seem to have come to pass and although not as prolific as I had hoped we are still getting new fruit. With a bit of luck we will continue to get tomatoes from the aquaponics setup for some time yet. In the dirt garden I expect that we are at the end of the season as the frosts are likely very soon.

Despite my earlier comments about lack of nutrients and light the vegetables have been quite productive.
We have had 2 separate batches of tat soi, several of lettuce, and good supplies of peas.
The coriander , in the picture with the beans, was a bit of a flop as it went to seed very quickly- Di reckons it was too hot at the time. Some of the other plantings also went to seed a bit quickly -perhaps for the same reasons. We also had rather slow growth with one of the lettuce varieties and the leaves were bitter so they were pulled out and fed to the chooks
We are currently getting a feed of beans about 2 or 3 times a week from about 30 plants- 10 in each grow bed- some are low as in the picture while the rest are growing on the supports I put in for the peas and tomatoes.
I have not really been a gardener before and so it is quite a thrill to be able to harvest fresh produce whenever I am in the shed.
All I need now is for the fish to produce MORE POO!
This is probably unrealistic now and I will have to wait for the warmer weather to return.

There is however the plan for a hotwater heat exchange unit for the fish- more later!!

An imagined problem and a solution?

Fish need oxygen to breath just as we do and they get it out of the water. The constant pumping of the water out of the tank and through the growbeds and back into the fish tank provides a lot of air to water contact which ensures the continuous exchange of gases.
It suddenly occurred to me a few weeks ago that if I had a pump failure for whatever reason, and I didn't know about it for some time, I only go over to feed the fish once a day, I could possibly end up with dead fish due to low dissolved oxygen in the water.
This is not really likely to be a problem at the moment due to the small size of the fish but when they are bigger it could be a very real problem. I imagine 200 plate sized fish need a fair bit of water/air contact to prevent them suffocating!
So I went looking for a big air pump- just like the ones used in aquarium setups but bigger.
It had to be at least capable of running on 12 volts and even better 12Volts and 240Volts.
I found one on eBay, bid and won, and a few days later it arrived.
I would not want to have it in a home aquarium setup because it is very large and quite noisy compared to normal aquarium pumps.
However it pumps about 40litres of air a minute and the box contains a 12Volt 7Ah sealed lead acid battery and charging circuitry etc which means that if the power fails it continues to run for some hours on battery power alone. I could also hook up a 12Volt input so that even if my inverter fails I can still keep the fish alive.
At least that is the theory!

Problems and solutions?

Although growth of the plants in the growbeds is quite vigorous they don't seem to be doing as well as I had expected.
I am reasonably convinced that I have 2 main problems:-
1. not enough light and
2. not enough nutrients.

So in an effort to solve or at lease improve on the light problem I decided to install the extra polycarbonate roofing I had bought at the beginning of the construction.
Taking advantage of a visit from my "nephew" I co-opted Gary into being a roofer's mate and we removed the zincalume roofing over the back part of the shed over the fishtank. This is a reasonably straightforward job despite the difficulty of trying to drive "one-shot" tek screws into polycarbonate sheeting whilst not putting any weight on the sheeting. Fortunately the sheeting is very strong and the occasional accidental step on it doesn't result in a crash through to the ground 4 or 5 meters below.

The fish don't seem to realise that the extra light is good for the whole system and they are currently much more skittish than they were before the extra light became available. I am hoping that they are just getting used to it and will eventually be more willing to be seen.

The not enough nutrients problem is almost certainly due to the fact that I have quite a lot of plants and not enough fish poo! There are probably over 200 fish but the biggest of them are still only about 100mm long- and a lot are much smaller.
So as mentioned in an earlier post I am adding pure Urea at the rate of 4g most days- this has lifted the nitrates to between 10 and 20ppm without causing any detectable ammonia or nitrites.
I was also adding chelated iron at the rate of about 5g per day for a couple of weeks. I was testing for iron in the water but not getting any detectable levels. However I should have been testing for the chelated iron and when I finally did so the levels were between 1 and 2 ppm. This is possibly too high a level so I am no longer adding iron. A test today suggests that the levels are a bit lower and I hope that the plants will take up more. As far as I can tell chelated iron is not toxic to fish and the fish don't seem in any way affected.

The fish are also eating less now due to cooler temperatures.
Temperatures in the shed are now a fair bit lower than they were in the middle of summer- not a surprise- as I write this the temperature outside is only 10 degrees Celcius. The tank was at about 15 degrees earlier today. The insulation I have around the tank is clearly helping to moderate temperature swings.