Which Filter?

[unspoken930]

Well, im getting two identical custom made 68 gallon tanks, made with 1/2 inch thick acrylic and black acrylic on the back yay! anyways, the guy who is making the tanks for me needs to know what type of filter to use. He can put in a trickle tower so i can use a sump with a canister filter attached, but because i want both tanks to be heavily planted, im afraid i will lose too much CO2 this way. I could also get the guy to cut holes in the back of the hood and make it so a HOB will go there, i really like biowheels, so they could work. Or, could i somehow have a sump that would pump water back up to the tank but have a HOB on it? i dont know, all i know is that the guy needs to know, and i need to save as much CO2 as possible.
Thanks for your help

 

[vic]

Saving CO2 is a twofold issue. First you must have a very efficient method of diffusing the CO2 in the water column. This requires some equip met to accomplish the diffusion of the CO2. I use an external in-line diffuser in the return line of an xP3 cannister filter. Easily built, out of sight and not taking space in the tank. The second issue is retaining the diffused CO2 in the water column for the plants. This crux of this issue is insuring that the water surface is not disturbed. The gas/water interface is driven by water movement at the surface and therefore if you are able to control surface water motion you are a long way toward the retention of the diffused CO2 in the water column. HOB's are very efficient and effective filters but they do significantly mess with the water surface and therefore aid in the release of the injected CO2 into the atmosphere. Internal filters don't have this impact on the water surface and the CO2 can likely be routed into the intake of the internal filter. This is not likely as efficient as a diffuser but will work relatively well. Using a sump provides the opportunity of also using an in-line diffuser however, the surface disturbance is again a potential issue. I have included a link to a very useful treatise on DIY CO2. I'm not necessarily suggesting that you use DIY, however the information about CO2 is very relevant.

http/www.qsl.net/w2wdx/aquaria/diyco2.html
I have also included a link to an in-line CO2 diffuser, a picture is worth at least a thousand words.

http/www.aquaticplantcentral.com/forumap...mp;d=1099597504