E-book discretionaries are confusing me

[Admin]

Thanks for your feedback! I’ll go back through the book and make those sections clearer.

Let me explain these biofilters in simpler terms:

• Small Biofilters: These are less than 3 meters (about 10 feet) long. They work well for small setups like backyard systems.
• Medium Biofilters: These range from 3 to 6 meters (about 10 to 20 feet) long. They are the most common size for medium-sized operations.
• Large Biofilters: These are longer than 6 meters (20 feet) and are used in large commercial setups where more filtration is needed.

You can choose whether or not to include a drainage pipe inside the grow bed. Here are some things to think about when making that decision:

• Sand Type: If your sand drains quickly, you might not need a drainage pipe. If it drains slowly, having an extra pipe would help.
• Slope: In a 6 meter grow bed, the shallow end is about 30cm deep, and the deep end is around 42cm deep. If you can’t achieve the right slope, extra drainage may be necessary.
• Experience: If you’re new to this, it’s a good idea to minimize potential issues by following the suggested guidelines.

We previously discussed using a slit drain, which is a great option for draining water because it pulls water sideways instead of pushing down on the sand. It also helps oxygen get in, drains water faster, and looks nice.

I really encourage you to stick with the slit drain. If you’d like, you can send us pictures, and we’re happy to help. If it were me, I’d cut a slot in the cinder blocks with a grinder, secure them with concrete, and cover everything with a protective liner.

Thank you once again for bringing this to our attention. If you or anyone else has any further questions or needs clarification on anything, please feel free to reach out to us.

[Robbet]

Thank you for clarifying the sizing, I thought it would be like that but the last wording confused me.

I plan on using the recommended 1:50 slope but I calculated the furthest end as 120mm the plan is then to go down 20mm per meter. I plan on first building the growbed due to space restrictions then digging the fish tank and adding the sand so I’m not sure what sand I am going to use but I’m definitely going to test the sample (I’m even considering buying expensive filter sand if it comes to it).

I’m not sure how I’m going to create the slope though so far the plan is to simply add sand into the growbeds base under the liner and try to have that sand with the correct gradient, my builder recommended I add a line horisontally connected to both sides and then to change the furthest end slope upward. Do you think that would work? I’m not sure how having a sand base is going to stay straight enough when I add the liner and adjust it.

I think trying to create the slit drain like that is above my ability to get right, but since you guys recommend it so much I thought maybe I could add 3 drainage pipes to minimise drainining pressure? Won’t be exactly the same as slit drain but should reduce pressure on sand, the main reason I’m not keen on a slit now is the pond plan is quite a distance from the biofilter and I’m not in the mood to try and figure out how to get the slit to drain so far.

Do you think simply having holes drilled in the cement blocks would be stable enough. I’m honestly not sure how I’m going to get the pipe through the liner without getting some leakage..

I really want to create the best filtration system I can so I’m assuming the main benefit of a slit drain is due to decrease in drainage friction the sand moves less and is thus more stable while also protecting drainage if one section would get blocked somehow?

[Admin]

I believe using damp sand under the liner could be effective in maintaining the slope, as I have previously tried this method with success.

Once you’ve installed the liner, you might consider running some water through the empty grow bed to verify the slope and ensure proper drainage before adding the sand. In my opinion, this is a crucial step for a straightforward and practical drainage test.

If you have any concerns about the slope or drainage, it may be helpful to consider installing a slotted ag pipe down the center.

Installing a slit drain is quite manageable, requiring a skill level similar to that of installing bulkhead fittings into the liner. An alternative could be directing the water from the slit drain into a gutter and then back into a pipe leading to the fish tank.

I believe the holes will be adequate, as bulkhead fittings should help prevent any leaks in the liner. There are plenty of informative videos on building ponds available on YouTube that could provide valuable insights.

A slit drain facilitates faster drainage, which is beneficial for the plants, allowing their roots to spend less time submerged. It also enables the ridges in the grow beds to function as ventilation stacks, drawing fresh air into the sand’s pore spaces.

If you refer to the ‘Vehicle Analogy’ section in the iAVs book, you’ll find that iAVs is designed to perform like a sports engine. Imagine building a sports car but using a lower-quality muffler or having a blocked air intake; while it may still function, it won’t perform to its full potential.

You could certainly implement three drains as you’ve suggested, although it may incur higher costs for parts and require more effort compared to installing a slit drain.

[Robbet]

Thank you for the insight, I’ll wet the sand before forming the slope for the added rigidness then I will add the liner secure it and finally make the holes within the liner.

I think I understand, so by having drainage spread out the ridges suck in air more vertically which is more efficient. Another factor is the drainage is faster which means the roots are less submerged which is good since too long submersion of roots is stressfull for plants. Or maybe the ventilation is simply better because the faster drainage means stronger air suction?