I’m putting this topic under “Algae” rather than “Plants”, although I was considering that this may be more of a plant health issue.
I’ve been running my tank without biomedia for many years now and, for purposes of pre-emptive questioning, the primary reason is to provide improved access to NH3/NH4 for plants while simultaneously reducing NO3 (plants’ preference for NH3/NH4 over NO3). For those interested; the nitrogen cycle can easily be maintained without biomedia in our filters, at least in a healthy planted tank with good biomass. I also have a heavy fish load.
However, I am now considering adding biomedia back in to my filter. While cruising, I stumbled upon this comment by @Edward
a few years ago:
Biological filtration is more important than people think. Have you experienced slimy leaves, glass or other submersed hardware or yellow gunk in outlet hoses? Then you don’t have enough biological filtration capacity.
Most companies make filter size recommendations of 2% or less per aquarium size. Ada Takashi Amano recommends 5% – 10%. The reasoning behind this is to have enough surfaces for beneficial bacterial to convert waste sludge to nitrate.
When there is not enough filtration then the aquarium becomes the filter. Surfaces become covered in slime and algae starts growing on it.
Of course, as I gradually reduced my biomedia, I was counting upon the biofilm to develop more fully on the surfaces throughout my tank, as I am sure that it did (and in the substrate), to take up any biofiltering slack that my plants couldn’t handle. Now, I’m wondering if some of the algae (mostly GSA) that we accept that develops on older, well-hidden, leaves may be a result of having this biofilm on the leaf surface. If this biofilm can be eliminated or, at least, reduced, do we also reduce the algae pest on these type of leaves?
Unfortunately, I can’t find much that supports this thought and am looking for a discussion that might expand my motive for putting the biomedia back in for this purpose. If anyone can provide some links discussing this (I can't find any of significance), I'd greatly appreciate it.
Of course, the biofilm is bacteria and the product of the bacteria might be a highly concentrated nitrogen source for algae, making it a preferred growth point for the algae. I would think that algae would also stick better to the biofilm than a surface not having it. If biomedia in a filter, being far more nourished with oxygenated water than the various surfaces in the tank, robs the BB in the tank of nutrients, do we get less biofilm on, e.g., our leaves? Does a leaf struggle if covered with increasing depth of biofilm, causing a cascading decline?
Lots of questions and some more:
- if we try to kill the biofilm in our tank (while protecting our biomedia), will algae struggle to develop?
- will leaves absorb nutrients better when not covered with biofilm?
- will biomedia, if sufficient in quantity, prevent any significant development of biofilm in our tanks?
- is there an allelopathic response from plants againts the bacteria?
- can algae even stick to anything without the biofilm first in place?