Backyard Aquaponics
A place to discuss aquaponics

I am curious and I can't find the info in one place here, what amount of water is required to flood a given size of gravel/media. Though I'd start a poll to gather data. Please list what your media is and the water to media ratio. I'm curious about larger gravel sizes and sand media. I'm running 1/4" gravel ATM, will measure it tonight for this poll...

It takes 13 gallons to flood my 50 gallon bed. I use a mix of about 30% hydroton and 60% 3/8" gravel.

Hi JP, if it is 13 gallons for 50 gallons of media should that be 25% for the poll choice instead of 50%?

Hi Dave
I get 50% with my aquarium top micro system, it has 3/8" (10mm) hydroton type stuff. I guess Janet didn`t vote yet

OK!

Some points to take into consideration on this:
1) the water level is normally 25mm (1") below the gravel level, so you can't just say I have 460 litres of gravel that is 300mm deep but put in 150 litres to a depth of 280mm - so use the water depth to the amount of media to that height

2) not all GBs drain fully so the amount of water left in the GB needs to be used in the calculations also

I use 20mm gravel on the base of the GBs to a depth of ~80mm then topped up with 10mm gravel - water to media ratio is ~40% (taking into account (1) & (2))

Hey Ell, I was thinking more about measuring that it takes x amount of water to flood x amount of gravel. I had thought about the wet versus dry gravel too, and since the normal operation is that the gravel would be wet I would measure it after at least one other fill.

Thanks for the data!

The percentage will only hold true for a short time due to the solids and roots taking up the space, 40% may become 30% or less after its been running for a while.
It might be worth checking the flow once a week to see how it declines and where/if it levels off.

Agree with you Hex - I measured my volume/GB last weekend and that was the figure from the media which has been in use constantly for over 12 months now

Needed to empty a sump tank so blocked up the GBs and bucketed in measured quantities of water for my own benefit...thus the reason why I mentioned water being left behind on drains and where the water level actually came too...from that I worked out my lph rate

Yeah, roots can take up an enormous amount of air space with some plants.. Mine have generally been around 40% air/water space when new, 200L of water to fill a 500L growbed. I've never tried to measure when filled with plants though..

This is one of the things I love about aquaponics when playing with different systems, it's not an exacting science as there are so many contributing factors it's impossible to take all things into account. You just have to allow fudge factors...

It looks like so far that you wouldn't see more than 50% and it will go down from there with time, so that's helpful info. Thanks people!

Ok so going by the poll results i should allow at least %40 maybe more to allow for roots taking up space

thanks for the info saved me a trip to the landscape suppliers

This info is also useful when figuring required sump tank volume. I usually use the 50% of grow bed volume though and then say to add some extra so that the sump tank will have plenty of capacity plus.

THis kind of information will be good for beginners so as to safely calculate the maximum number of Gb's in a system.... I can see how a person can get carried away and try stretch their water too far amongst their GBs... The reason for me experimenting lately is to ensure that I have at least 300L of water in each 'in-ground' IBC when the pump is running... I have come to realize that i need another IBC connected to the 2 in-ground ones in order to run the number of GBs I want to...

When I have conducted the second phase of my tests I will vote and post more...

I have 1500L tank running through 1 ton (not all at the same time) spread over 8 GB's, I am attempting to add another 10 GB's soon so figure there will be at least another ton of media.
AM might be right in suggesting It's streching it too far but me being me I will give it a go.
The GB's atm flood in 10 mins and they are 1/2 blue barrels (100L), all I have to work out is the water flow rate from the pump