Backyard Aquaponics
A place to discuss aquaponics

Hi,

I'm looking at using vermiculite and perlite mix in GB. My question is, how long will the mix last? I assume I'll need to have longer flood and drain cycles, to prevent it getting waterlogged. Also, is the weight of the dry top 5cm of media enough to hold the vermiculite/perlite mix down?

Thanks
Rob.

Most people that try perlite take it out later. It works well in non return gb's.

It'l float and be horrible, please dont do it

I agree with OBO- perlite is probably not the best choice for AP in most cases. In my trials, perlite floats and leaves the containers, which can cause problems elsewhere; it attracts algae growth and unless you want to pay for commercial grade perlite from a horticultural store, you can only buy the small broken stuff locally. The only place I would suggest perlite (commercial grade only) is in vertical towers and secure the top of the tower with netting and/or gravel. The only reason I am suggesting it there is because of it's light weight and excellent wicking abilities.
Also don't use peat of any kind in your AP systems- it can contain Pythuim fugus spores, which can wreak havoc in the moist conditions during the summer months. Alberta Canada has been trialing systems similar to UVI's and that has been one of their biggest problems- attacking tomatoes and cucumbers and UVI has also had problems with it in their 2nd cuttings of basil.
In my next seedling experiments, I'll be trialing vermiculite to see how it reacts to the three growing types of DWC. If that doesn't work well, then I'll grow my seedings in very small rock- at least I know that will sink to the bottom and not be an issue, as even sand can float.
What I am looking for is something that can start seedlings and then the entire container can be transferred into a DWC raft- it would create the least stress on the plant (less transfer shock), the easiest to work with (no manipulation of the plant, container or media) and free up my ponds for conveyor style finishing and harvesting (seedlings are the biggest area of culling). I am looking into a commercial system and for me that means the least amount of labor but the maximum amount of production.

A typical hydro seedling mix is vermiculite:perlite... in a ratio 75:25... works great as a seed raising mix... but usually intermittently watered...

I did try using a mix like that in flood & drain... and it was at least stable compared to perlite...

But still was too wet... in the same way coco-coir is...

F&F... used the same ratio mix... for good results... but I think with an intermittant watering system..

Just straight vermiculite 15 min on 2 hrs off

I keep saying this - covered with 3-4" of gravel, with gravel around the standpipe, perlite works exactly like gravel over 2+ years, 15min on every 1.5 hours.

If you want a lighter weight bed with less washing than gravel, either give it a go or pay for hydroton.

I think I've said it enough times now

Great, thanks everyone. So if I go this route, as f&f and steem point out, I'll need to have a much longer "dry" time, so less water circulation for the fish... I'll weigh up the options tonight. Thanks