A Basic Approach to the Natural Planted Aquarium--Part Three
A Basic Approach to the Natural Planted Aquarium—Part Three
In Parts One and Two I discussed plant requirements respecting water parameters, substrate and nutrients. In this third instalment, filtration will be described.
Filtration: Aquarium filters usually employ three types of filtration: mechanical, chemical and biological. A well-planted aquarium with a balanced fish stocking actually requires no additional filtration beyond the plants themselves; however, most of us like to have more fish, and mechanical filtration is practical for maintaining water clarity. This is not the same as “cleaning” the water, the task best performed by the plants in what Dr. Ted Coletti terms “Vegetative Filtration.” The filter will keep the water “clear” of minute suspended particulate matter by passing the water through media like disks and pads or filter floss. There is no useful purpose served by chemical filtration, and there is evidence that carbon and some other types of media remove plant nutrients, so a planted aquarium should not employ chemical filtration. Biological filtration occurs on all hard surfaces within the aquarium, considerably more than in the filter. As was mentioned in the discussion under “Nutrients” in Part Two, biological filtration in a planted aquarium may likely be detrimental to plant growth.
Mechanical filtration is therefore sufficient. In smaller tanks, less than 50 gallons, I would use a sponge filter. In larger tanks, a canister works best; it provides good mechanical filtration, and the flow can be directed and often regulated. The rate of water flow determined by the filter provides the water current within the aquarium, and this should be suited to the requirements of the type of fish in the aquarium. Those from running streams should have a suitable current from end to end to replicate their habitat. But most of the “forest fish” that we house in planted aquaria occur in quiet streams, ponds, swamps and flooded forest where the flow is minimal or almost non-existent, and such fish will feel less stressed in a calmer environment and thus be healthier. And there is also an impact on the plants from water flow that must not be overlooked.
The filter should produce a water flow sufficient to ensure the water circulates through the tank and filter. This is important for bringing nutrients to the leaves and roots, and keeping the leaves free of sediments. The rate of water flow through the filter also has an impact on the amount of oxygen drawn into the water, and the carbon dioxide (CO2) expelled from the water in what is called the gaseous exchange. Surface disturbance speeds this up, as do higher flow filtration, air stones, bubble effects and power heads—devices that should not be incorporated into a well-planted aquarium. Plants produce considerable oxygen as they photosynthesize, more than sufficient for the needs of the fish and bacteria. Extraneous water movement is detrimental in two ways: CO2 which is extremely important for plant growth is driven out of the water faster, and oxygen is brought into the water at levels beyond what is good for the plants, which have more difficulty assimilating nutrients when the oxygen level increases. This is because oxygen easily binds with many nutrients, such as iron, making them too large for assimilation by the plants. But the more significant aspect is the loss of CO2.
As plants grow they assimilate CO2 and produce oxygen; in a biologically balanced aquarium, the amount of oxygen produced during photosynthesis is considerably more than that used by the plants and fish even during the night when the process is reversed, so there should be no concern over oxygen depletion requiring more filtration. Submerged plants have difficulty obtaining enough CO2 in nature and in the aquarium; this fact is believed by many to be the reason for the inherently slow growth and low productivity of aquatic plants over terrestrial. Further, freshwater emerged plants have been shown to be four times more productive that submerged plants. The reason is because CO2 diffuses so slowly in water as opposed to air, and this limits the underwater plant's uptake of CO2 because the CO2 molecules don't contact the leaves quick enough to meet the plant's needs. Aquatic plants have to use enzymes to rapidly capture the CO2. When the CO2 levels in the water become depleted, these enzymes sit idle, so to speak, but the plant still has to provide energy to them. This results in a reduction in photosynthetic efficiency and therefore growth of the plant because energy is being wasted. Thus, anything that removes CO2 in however small an amount will be detrimental to the plant's growth.
In a natural or low-tech system, the balance between the 17 nutrients (one of which is carbon) and light has to be there; so anything that may impact however slightly can become a critical factor in less success. The one thing we cannot "control" in this type of setup is the CO2, by which I mean that it is entirely dependent upon the fish and biological processes; with light we can control it, in intensity and duration, to balance, as we can with the other macro- and micro-nutrients through fertilization. Plants will photosynthesize up to the factor in least supply. Many have planted tanks that fail because the CO2 is the limiting factor, and algae will take over because it is better able to use carbonates for carbon than most (but not all) plants. The point here is that nothing should be allowed to negatively impact the CO2 in the natural planted aquarium. For this reason, filter flow should be minimal and surface disturbance as little as possible. The plants will then be able to fully assimilate the nutrients.
The final Part Four will discuss the single most important aspect of a planted aquarium, light, and on-going maintenance.
 Ted Coletti, “Back to Basics, Part II: A Multi-Modality Approach to Livebearer Aquarium Filtration,” “Livebearers Unlimited” column, Tropical Fish Hobbyist, July 2009, pp. 34-36.
 Peter Hiscock, Encyclopaedia of Aquarium Plants, 2003, p. 29.
Diana Walstad, Ecology of the Planted Aquarium, second edition 2003, pp. 93-95, 104.
 Walstad, idem, p. 163.
Good posts Byron. I'm particularly interested in the biological filtration. Considering biological filtration other than what is provided inside the tank isn't needed in a heavily planted tank then I assume, perhaps, that the bio disks in a canister filter should not be used. If that assumption is agreed with, then would a canister filter in a 55g be overkill? I'm thinking, considering the cost, if one wants to use a canister filter with media for removing free floating particles is there a more economic and similarly beneficial way to achieve this?
I was going to use a canister filter minus the chemical filtration. However, why spend that kind of money if all that is needed is a decent form of debris collection? But a power head with a filter attachment may also be "too" turbulent. Any filter suggestions? HOB? I've used them before in concert with an UGF, which will not be in play this time around.
When I had a 55g in the 1980's I had first an UG and when I took that out I used a HOB that had a directional outflow spout that was great because it could be directed at the end wall and significantly weakened the flow. I just had filter pads/floss in it. I wouldn't go this route now though, as there are better oprions with canisters and sponge filters that I didn't know about back then.
I have a small sponge filter in my 33g, and were I to set up a 50g I would use a sponge filter. Maybe two, depending upon size. I believe Angel has done this too. B.
Not sure if its ok to comment in a sticky note? :-? Otherwise pls del it Byron, I think you can del posts as Mods and I'll just PM Harri...
In 55g's I went 2 ways: Either set up a Eheim 2213, which you can get for a good price incl everything needed here EHEIM Classic External Canister - Filtration & Circulation - Fish - PetSmart
Which worked well for me in planted and heavily planted tanks with large stocks or medium stocked.
The 2nd option I learned and chose overseas for planted tanks, is a DYI sponge filtration system that works wonderful, just googel results for 'Hamburger Matten Filter'. Its the same concept then the mini sponge filration that one would chose for a smaller tank, but building it the height of the tank in a corner obviously for 1 allows for a larger filtration area 2) Using a small water pump (such as found in the homes store for these indoor water fountains) makes for a flow good enough to keep the tank clean but at the same time not heavy to hinder plant growth 3) being set up with that very pump eliminates the "bubbling" sound a normal sponge filter will create you 4) if you have any shrimp in this tank with a HMF filtration they're gonna LOVEEEEE this snack bar :-)
I couldn't put my finger on which one I liked better, both done the job I needed them to, both worked well. "Downside" if any 1) the Eheim needs some cleaning about 1xyear, the HMF didn't. 2) The HMF being a DYI with a supply list of 3-4 items is easily set up at about 1/3 of the cost (if bought a Eheim for $70 in comparison) 3) The HMF is not easy to add in a exiting running tank, so there the Eheim would be my choice, or is you're simply not liking DYI projects, again Eheim is easier.
Hope this is enough info to make a decision (if not pls PM me so I don't clutter up Byrons planting guides :| )
Great post! Thanks Byron!
Oh wow. Good information. I did not know that Chemical filtration could be slightly detrimental to plant growth!
Thanks for all the info.
I think one can argue that movement of water actually helps the plants take in CO2:
For the aquarist, the supply of CO2 can be augmented in two ways. Both methods work by increasing the rate of diffusion of CO2 into the plants. First, the rate of water movement in the aquarium can be increased. This will decrease the thickness of the boundary layer and ensure that CO2 levels are at air equilibrium. This method is inexpensive, easy to implement and will produce excellent growth of aquatic plants under most conditions. Secondly, CO2 can be injected into the aquarium. This method can be expensive, and if done improperly, can be lethal to fish. This latter method is only essential, however, if there is a significant daily pH fluctuation in the aquarium, or if the species of plants being cultured are completely unable to use bicarbonate (such as Cabomba sp.).
Thank you for the series of articles. I've had so many questions and have read so many conflicting things..this really was informative.
thank u :)
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