CO2 generating substrate
As requested, here's the original post that I made on my favuorite Ozzie aquarium forum, Aquarium Life, and the link (
http://www.aquariumlife.com.au/showthread.php/30650-Cheap-Sand-based-CO2-Generating-Sub) for those who are interested:
"Here's a recipe I've been using for 4-5yrs (now 8yrs) for a low cost, long life substrate that suits just about everything I've grown.
- Propagating Sand (Brunnings $4.95 a bag)
- Marble Chips/Oyster Shells
- Blood & Bone
- Laterite (optional, as the sand has a lot of clay in it)
- Peat Moss (optional)
Cover the base with 1-1.5cm unwashed propagating sand - straight from bag, heaps of clay
Sprinkle marble chips - 1 x handful per 30cm square
Sprinkle blood & bone - 1 x dessert spoonful per 30cm sq
Sprinkle laterite - 1/2 x handful per 30cm sq or lay cut and dried potters clay
Cover the lot with 3-4cm well washed propagating sand, don't want all that clay in the water column!
Cover with cling wrap and fill to desired level to work with plants.
The propagating sand is full of minerals and a fair bit of clay... that's why you can get away without using laterite. Coupled with the B&B for N & Ca, the gross feeding plants love it.
The marble chips help maintain ph balance, which is needed for efficient nutrient uptake, and provide an ongoing Ca source. It also acts as the carbon reserve, supplying CO2 as it dissolves. Oyster and other mollusk shells do the same and are the building blocks of aragonite.
The sand is fine grained for a substrate, which keeps all the crap from leaching into the water column. But it really encourages micro-organisms, worms, etc... and I find that the spiral (Malaysian) snails keep it really well aerated - not to mention the Corys rooting around.
In three years I've never had a problem with fouling or gas build up.
I've tried adding a fine layer of peat, but haven't noticed an appreciable difference either way.
The substrate in my shrimp tank is full of tubifex, which aerate it constantly and transfer nutrients up and down through it. My CRS/CBS seem to love the free treats they deliver.
Give it a go - even in an experimental tank."
I might add that this sub is now in use by 00's of hobbyists and, as the thread on AL shows by its popularity, has proved its merit. The recipe was one I settled on after many years of trial & error and initially inspired by the writings of Diana Walstad, the renowned aquarist - thank you Diana!
I've since found, thanks to the work of another AL member and good friend, Mark Bear (Bardus), that increasing the depth of the sub to a total of 7-8cm gives the added benefit of a Deep Sand Bed that provides anaerobic bacteria the opportunity to convert nitrate to nitrogen & oxygen therefore, completing the final process in the
nitrogen cycle. As such, and because I currently use rainwater in my tanks, I don't actually do water changes as part of my husbandry, just top up.
Cheers, Tony
