Figuring Out Filtration With Plants

[xxEMOxLIZZARDxx]

Alright, I've got no idea where to search so I'm asking here.
 
I've got a 30g tank that my dad has taken over for me (I moved out of state and don't have room for it). We've got four what look to be Amazon Sword Plants that are about six inches across with between ten to twenty leaves on each, one Red Flame with two leaves on it and two Moss balls.
 
I think we've got a filter rated for 30g, but I'm planning on picking up two 40g since the one we have seems to be tanking out.
 
I'm attempting to figure out how much the plants are bringing to the table. I know they can help with filtration, but I've never been able to get a precise number.
 
I've currently got 5 Platy's, 5 Mollies, 9 Guppies, 5 Harlequin Rasbora's, 3 Juli Cory Cats and 1 Pleco. I don't know what species, my dad bought it even though I said not to buy it. He said the guy said it wouldn't get big. No more than three inches apparently.
 
I know this tank is most likely overstocked (I'm planning on a few fish dying because my mum loves to overfeed and my dad isn't great at remembering water changes. I know, I shouldn't plan, but I do).
 
So, can someone help me figure out how much the plants are helping with filtration? Because I'd really like to know.

 

[DrRob]

Plants do help with filtration, they take up ammonia and nitrate, amongst other things, that would otherwise end up in the nitrogen cycle.
 
Quantifying it is difficult however, and tanks that rely on plants for filtration generally rely on fast growing stem type plants, rather than the crown type plants like swords as they tend to pull a lot more nitrogenous nutrients in a short period of time.
 
Overall it's probably best to ignore them when calculating the filter, apart from the fact that, to grow well with no algae clogging them, they'll need good flow over them and that often means that you need a bigger filter than you expect. Heavily planted high tech tanks generally quote a need to turn the contents of the tank over 10 times an hour to keep the plants healthy, which is far more than most filters are specced for.

 

[Byron]

This is something I have researched a while back, and I am on much the same page.  Obviously one can have a tank with no "filter" (meaning equipment we use) and I have done this, but most of us tend to overstock fish so this can push the system over the edge if not careful.  So, we will agree that a filter is advisable.
 
There are however two aspects to filters which are very different, and this is important here.  First is actual filtration which can be mechanical, biological and chemical; the second is water flow.
 
Taking the filtration first, you do not want any type of chemical filtration in a planted tank, except in an emergency; chemical filtration involves the use of some "chemical" or property to alter the water chemistry.  Carbon is the most common.  These substances will remove plant nutrients, and particularly DOC (dissolved organic carbon) which is a major source of carbon for plants in an aquarium, and this nutrient is often the one in shortest supply, so you don't want to be further deleting it.  Biological filtration is not really necessary, as the plants do this better (provided the tank is in balance) but nitrifying bacteria will colonize all surfaces in the aquarium anyway.  Dr. Neale Monks has written that there are more of these in the substrate in an established aquarium, so biological filtration in a filter does not need to be emphasized.  It will occur regardless.
 
That brings us to mechanical, which is the movement of water through media and pads to remove suspended particulate matter (much of which is microscopic), and here we cross over into the flow issue as well.  This is essential to keep the water clean so plant leaves do not become home to sediment which blocks the exchange of nutrients.  At the same time, too great a flow is detrimental because it moves the nutrients in the water past the leaves too fast and the uptake of nutrients can be hindered.  CO2 for example take about four times as long to be assimilated in water than in air.  Some plants also struggle in strong currents; I have killed Echinodorus (sword) plants in front of a strong filter return, when the same plant species thrived further down the tank in calm water.
 
The other aspect is that overstocking a tank is not going to be helped by more filters, once you are at a certain point.  Chemical substances accumulate in the water and no filter can remove some of these.  Plants can, but this is quite limited when we are dealing with overstocking.
 
I have seven tanks running presently, and one is a 30g and this one has a dual Elite sponge filter.  But the fish load was less than what you describe.  I would confirm exactly what your pleco is, as these fish produce a lot of biological waste.  I don't know what filter you have, so it may be sufficient and the next up may not do much more anyway.  But more flow with the fish load is probably a good idea.
 
Byron.

 

[xxEMOxLIZZARDxx]

Hello there,
I apologize for not responding right away. I kind of forgot about this account.
So best bet is to not include them in trying to figure out filtration. I already don'thave any charcoal in the filters, I'm not even sure if there is any batting or anything in the filters because after a few times of rinsing them, they all fall apart.
Also, I've got TopFin filters. One is a TopFin 60 and the other is a TopFin 30.

 

[TwoTankAmin]

I always had a simple way to check if a tank was fish safe in terms of ammonia. I added ammonia to the tank and then checked to see how fast it disappeared.
 
But I will comment on what others have not. First, Amazon swords grow quite large. I had one outgrow a 75 gal. tank.
 
And then, the answer to your question is not a stable one. By that I mean plants grow. So if you start a tank with a few 6 inch swords, they will use as many nutrients as they need. This will include having enough energy for growth. Now a few months later these swords might be 10+ inches and three months from then 15+ inches. A 15 inch sword can use much  more nutrients than a 6 inch sword. And this is where the need for bacteria comes in. It will fill in any "gap" left by the plants.
 
The other side of this coin is, you can start with smaller plants and if you start by stocking very lightly, you can ramp up the stocking gradually in concert with the increase in the plant biomass. As noted above,
 
I also advise that you plant the tank and get the plants established before you begin stocking. That way those with roots will have time to settle in and be less likely to uprootable by fish.
 
I always went the bigger plant/biomass route when setting up a new tank. I used plenty of plants, many fast growers included, as well as some cycled media. I have fully stocked tank many times simply b using this method. I set up the tank and when I finished, I added all the fish. But, I knew what I was doing was 100% fish safe in terms of cycling related issues. One thing you can do is to start out with a lot of the fast growers and once the tank is finally well planted and fully stocked you can begin to remove a few stems and replace them with other plants you would like to have. If you do this every couple of weeks it should be safe for the fish. However, I suggest one always have some fast growers in a tank.

 

[TwoTankAmin]

I should have tacked this on above relative to Byrons comments about nitrification in planted substrates. This one looked at the difference between planted vs unplanted substrate.
 

 
Nitrification and denitrification in the rhizosphere of the aquatic macrophyte Lobelia dortmanna L.
 
Nils Risgaard-Petersen’ and Kim Jensen
Institute of Biological Science, Department of Microbial Ecology, University of Aarhus, Ny Munkegade Bldg. 540,
DK-8000 Aarhus C, Denmark
 
Abstract
Nitrogen and 02 transformations were studied in sediments covered by Lobelia dortmanna L.; a combination of 15N isotope pairing and microsensor (02, NO3-, and NH4+) techniques were used. Transformation rates and microprofiles were compared with data obtained in bare sediments. The two types of sediment were incubated in doublecompartment chambers connected to a continuous flow-through system.
 
The presence of L. dortmanna profoundly influenced both the nitrification-denitrification activity and porewater profiles of 02, NO3-, and NH4+ within the sediment. The rate of coupled nitrification-denitrification was greater than sixfold higher in L. dortmanna-vegetated sediment than in bare sediment throughout the light-dark cycle. Illumination of the Lobelia sediment reduced denitrification activity by -30%. In contrast, this process was unaffected by light-dark shifts in the bare sediment. Oxygen microprofiles showed that 02 was released from the L. dortmanna roots to the surrounding sediment both during illumination and in darkness. This release of 02 expanded the oxic sediment volume and stimulated nitrification, shown by the high concentrations of NO3,- (-30 FM) that accumulated within the rhizosphere. Both 15N, isotope and microsensor data showed that the root-associated nitrification site was surrounded by two sites of denitrification above and below, and this led to a more efficient coupling between nitrification and  denitrification in the Lobelia sediment than in the bare sediment.

from http/m.m.aslo.info/lo/toc/vol_42/issue_3/0529.pdf