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 Post subject: 1500l round fish tank
PostPosted: May 6th, '20, 08:26 
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I have a 1600L or 440gal fish tank and im wondering how much media i will need for this size. Im not planning on filling it up to the top so will be more around 1200L roughly. I am also planning on stocking it with blue tilapia, I was thinking around 40 of them. I only have a small growing space so this tank size may be a bit much i am just hoping the lettuce and herbs will absorb enough of the nitrates so as to not kill the fish.


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PostPosted: May 7th, '20, 08:00 
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Welcome to the forum

For 40 fish, grown to plate size (about .5 kg each) you need about 800 to 1200 litres of wet media. That is based on the principle that each fish needs 20 to 30 L of wet media.

Fish tank size is a bit less important... you probably need a tank that big for all your fish. Just need to make sure your pump can turn your tank volume over every hour or so.

The above figures are rubbery... rules of thumb. Tilapia might be able to tolerate more crowded conditions.

You can manage with less media, but might be fighting ammonia spikes early on and, unless you can squeeze in a lot of plants, high nitrates later

Search on this forum for more info. There's a thread called "rules of thumb", or something like that. Look up "stocking rates" too.

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PostPosted: May 7th, '20, 08:03 
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I should have added that nitrates are unlikely to bother you fish, unless very high. It's the nitrites and ammonia that can be the problem.

Again, there's lots of info on the nitrogen cycle in this forum.

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PostPosted: May 10th, '20, 03:52 
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Thanks a lot for getting back to me dave! My growing space isnt very large. I actually have 2 440 gal tanks. 1 i am going to put the fish in one and the other i was going to fill with hydroton and use as a grow bed. Also will be adding around 6, 5 foot vertical grow towers that i am currently building. Will mainly only be growing lettuce to sell to a couple local restaurants and for friends/family.

How would you recommend i heat the fish tank water if needed? I was looking at purchasing maybe a few aquarium heaters but not sure if this would even work.


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PostPosted: May 10th, '20, 04:23 
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I'm guessing that your grow bed will be a lot deeper than the standard 30 cm. You should be able to avoid ammonia and nitrite spikes with that much media. But, if you have 40 fish, will probably not have enough growing space for enough plants to handle the nitrates, even with the vertical towers.

I don't know for sure, but suspect that a very deep grow bed could come with challenges. Not sure how well a very tall siphon will work. Or how well oxygenated water will reach all parts of the media if running constant flood.

I had a small undercover system with a fish tank heater. It kept the water about 4 degrees C warmer than ambient. But the tank was very well insulated. And I'm in a semi-tropical area so winter temperatures only get down to minimums of about 12 C overnight. And it used a lot of power. Unless your electricity is very cheap, it will will probably cost more than you will get from selling a few leafy greens.

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PostPosted: May 10th, '20, 07:18 
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Do you think I would be better off using 55gal food grade barrels cut in half for the grow beds? Ive done this before on a much smaller scale. I figured I was going to lose money with this set up considering i have to use led lights,water pump, maybe a water heater but this was mainly for the experience before I do a larger system. There are no aquaponic businesses anywhere near me with a population of over a million people, plus i have good connections to be successful in the long run.

I could try using rainbow trout but i know they are a challenge for beginners. I dont need to use 40 fish either it was just a rough number. I got the 440 gal tanks because they were only $200 canadian each. The room i am building will be insulated but its only about 11' by 20'.

Does the amount of water dilute the nitrates produced? Im not sure how to explain this...like would i just be better off using smaller fish tank or less water or does it not matter? I imagine i could just use goldfish but i wanted the experience growing fish u can eat instead of goldfish again lol. Thanks again for your input! Sorry im a bit difficult to follow(adhd) lol.


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PostPosted: May 10th, '20, 08:12 
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This forum is mostly about backyard (hobby) aquaponics. And I'm reluctant to be giving advice when you're planning to go commercial eventually. But it's a great idea to do a trial system at small scale to start... because I suspect there are lot of people who have found aquaponics doesn't work as well at a commercial scale as hydroponics.

That said, there are some people on here who will be able to give good advice... and some lengthy threads from people who no longer or rarely post but who were (may still be) doing commercial scale. Have a look for Chatterson Farms and a poster called TCLynx.

As for your further questions... and I might be mistaken, but I suspect you'd benefit from doing some reading about the nitrification process, cycling, common setups - and have a look at the IBC of aquaponics if you haven't already. It's really worth having a bit of knowledge before jumping in.

When you next post, let us know how you intend to run your system (constant flow/flood vs ebb and flow with pump on timer vs bell siphon). a rough diagram can be helpful.

As I say above, and others might correct me because I don't really know for sure, I wouldn't have a grow bed much deeper than 30 cm... so you might use that extra tank as a sump tank... or save for when you expand the system.

The 200 L drums would probably work as grow beds if cut lengthwise... I can't guess their dimensions. But that will mean lots of plumbing. You can probably only have about 3 fish per growbed if using them.

Indoor systems can work... my Murray Cod system was undercover but enclosed so ran with grow lights. wrt heating, heating the water is complicated by the fact that most of the heat is lost each time the water is turned over through the grow bed. So the temperature of the room you have the system in will impact on how many (or how large) water heaters you have.

You need very few fish to grow lots of salad (do a search on stocking rates)... better to start off lightly stocked - I know because I didn't :wink:

Tilapia seem like the perfect beginner fish... we can't have them in Australia. They'd be perfect for aquaponics but we have big fines for keeping them because they're a pest species.

More water in your tank will keep your fish happy... and the bigger the volume, the more stable your system will be. Remember that you need to have a pump big enough to turn the water over reasonably regularly... I think roughly once an hour is ideal.

Yes... if the volume is bigger, then the same amount of nitrate will be more diluted. But it won't really help you in the long run if you don't have enough plants to use it up as fast as the fish and bacteria produce it. As I said earlier, nitrate is far less of a problem (for your fish) than nitrite and ammonia. My nitrate has been off the charts for a very long time and I haven't noticed problems with my plants... but the real experts on here will tell you that it can cause problems... iirc, things like leggy and bitter tasting plants and maybe an off taste in your fish... it's not an issue for me as a hobbyist but it would be a concern if I was wanting to make money.

Enough for now. Happy reading and planning :)

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PostPosted: May 16th, '20, 13:23 
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Thanks for all your input Dave. I really appreciate it! I will try to explain what im working on in more detail sometime this weekend( or through the week at the latest) as well as show a diagram of what im thinking to build/ pics of the area.

I believe I can make the aquaponics successful in contrast to hydroponics. In Canada aquaponics is considered organic and hydroponics is not so that is a bonus for marketing. Even tho certified organic is a bit of a joke here at least i can still say it is organic. The price of fish feed here is also cheaper than the nutrients used for hydroponics. I am aware a few minerals will have to be supplemented but I have found a cost effective way to do this. I will mainly be selling to higher end restaurants and distributors in my area as I grow bigger which shouldn't be hard to secure due to lack of competition as well as having a great network.

I do have some knowledge in aquaponics surprisingly lol. I attended a 3 day class last year and have done barrel ponics for about 6 months now with a few 200l barrels and goldfish. It gets more complex the bigger it becomes, couple areas im struggling with but i just need the hands on experience i learn beter that way. I have no background in farming or business and although its been a bit of a steep learning curve, i have been enjoying both( except making a business plan, not much fun lol).I have a strong desire to give back to my community as much as possible with this venture, which is very important to me. I need to make sure things go smoothly by starting small and growing bigger gradually. I am fortunate to have a couple wealthy family members who are willing to invest as well to help me out down the road.

Ive decided to make troughs for the media bed out of wood and pond liner instead of using the other fish tank. Do u have any reccomendations as to what liner I should use? EPDM? PVC? HDPE? Or what about the liquid rubber which i think can be neoprene which i believe is food safe. Ive been looking into what is best to use online but have found no definitive answer yet. Seems more like personal preference. Also, havent been able to find any that are labelled food safe or food grade so far. Mainly been looking at local hardware stores/amazon.ca.

Take care for now,
Sean


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