Hi,
Yes, getting flow to the substrate is always difficult and that's why I like to use spraybars connected to very muscular filters (in concert with external in-line diffusers) to help shape the circular flow towards the bottom of the tank. The bars don't have the most elegant look but you can place them almost out of the water to hide them, especially if you get the dark smoky colored ones.
That's a really good idea that you have with sending the bubbles into the Tunze. You can play with the pump placement to optimize contact time.
DHenry said:
Other than the HC having lost weight and getting the algae in it, it has grown new leaves and they are nice and green. Much smaller than the ones it had though. Without having actually seen it would you agree that the loss of weight would most likely be a deficiency in Co2 as opposed to nutrients?
Yep, when troubleshooting health problems always start with the most basic and fundamental known properties. In a way that's like committing your multiplication tables to memory so that it becomes automatic.
Here is your 2X table:
"In our tanks, Filamentous algae is only ever caused by poor CO2."
So automatically you know that you have poor CO2 when you see this type of algae.
3X table:
HC as well as just about all carpet plants has a very high CO2 Compensation Point. This means that they require more CO2 just to survive than other more robust plants such as ferns or swords.
So automatically you know that if your focus is to grow carpet plants you must optimize your setup to cater to this weakest, least efficient of CO2 feeders.
4X table:
Over 40% of a plant's mass is made up of Carbon, which is integral to growth. Any anomaly affecting plant mass or structure is due to a failure to assimilate Carbon. Anyone who's been on a diet knows that the fastest way to lose weight is to cut out the Carbon products such as sugars and starch.
The combination of the factors that you have observed (or at least what you have reported) in the tank leads you immediately in the direction of CO2 without even having to think about it. This does not mean that you don't have other problems as well though. You could easily have both a Carbon problem as well as a nutrient problem, however, nutrient problems will have their own automatic multiplication tables. This enables you to look at the tank and to draw the right conclusions regarding cause and effect.
Cheers,