Too much Bio-Media?

[snickle]

I have a 90G with built-in overflow feeding a wet/dry filter (with a massive bio-media area). The tank was well-established before going planted.

The stocking load has not changed significantly since I went planted.

Doing some testing on frequency of water changes, since the tanks has been planted. I notice, that if I let it the Nitrates climb to about 40ppm and then level off. I am assuming the plants are consuming the nitrates at that point.

I was reading Diana Walstad's "Ecology of the Planted Aquarium". She suggests that plants prefer Ammonia and Nitrite to Nitrates as a source of Nitrogen. And suggestions reducing the amount of bio-media in the canister to allow the plants to receive more of the simpler form of Nitrogen.

If it is true that the bacteria can out compete the plants for the raw forms, and then the plants need to breakdown the nitrate, then my wet/dry setup is probably making it harder on the plants.

Would it be worth removing the a large percentage of the bio-media and let the plants get more of the raw nitrogen?

Thoughts?

 

[Aylmer]

As far as i know everything in the tank competes for everything. Its a delicate balance which is achieved by trial and error. If your tank itself has a good setup of beneficial bacteria, reduce the % of the bio-media. I feel a large % change could disrupt the balance, too fast too soon kind of thing. Keep your deligent observations going and an answer would appear.

 

[Squawkbert]

Probably, but then, when it's time to do a significant trimming of plants, NO2 uptake slows and stresses the fish (mini-cycle).

Plants are tougher than fish, so I'd keep the biomedia, especially if you like to have more fish than what your plants can handle (like 99.5% of keepers do).

 

[geofied]

You likely don't need the amount of bio media you have and as you are aware it may be literally eating some of your plants preferred nutrients. Don't forget that the substrate, plants, wood, rocks, everything in your tank is a potential storage area for de-nitrifying bacteria too. I would suggest removing a little each week as opposed to big chunks at a time, if you do decide to remove it.

This may prompt me to look at my bio media too, forgot to reduce mine after seeding my new tanks with used media to avoid cycling (which worked both times I've tried, by the way).

 

[snickle]

I will leave the media in the filter this weekend, as I am removing al lthe substrate and replacing. Once, things settle down again, I will start removing bio-media. I have about a cubic foot of tightly packed potscrubber as bio-media.

I can dump enough ammonia to bring it up to 1 ppm and have the it drop to 0 ammonia and 0 nitrites with in 5 minutes.

Yes, I removed the fish before testing.

 

[Canuck]

Your assuming that the amount of bacteria is constrained by the availability of Biomedia (I doubt this). The amount of bacteria is more likely constrained by the amount of ammonia and nitrite. Decreasing the size of your biomedia is only going to increase the concentration of bacteria on the available surface areas and your plants will have the exact same amount of ammonia available to them. This of course assumes you don't add more plants to soak up more ammonia, but then the amount of ammonia per plant still doesn't increase.

Another thing that I'm not sure you've considered is Walstad's theories work best in a slow growth tank. Does this describe your tank? I think most of the plant gurus suggest algae loves ammonia and its quite likely a decrease in biomedia may mean more available ammonia and an increase in algae. Algae loves fluctuations in the environment and thrives under these conditions. Plants prefer consistency.

Just food for thought.

 

[geofied]

Canuck, I hear what you're saying, but I think one important part to remember is that if the additional bacteria in the filter media are eating/converting the nutrients, there are potentially less of those nutrients available to the plants. I would venture to say that since the filter is, by nature, the most frequently traversed area (by design), then reducing filter bacteria will allow the plants a better shot at getting those nutrients as the filter bacteria will not be "hogging" them. Even if we were to suppose that the bacteria in other parts of the system would grow to meet the increased demand, it is unlikely that they would be as efficient as the filter bacteria.

I agree that once you achieve a balance of sorts, you're at risk when you change too many things at once, so again, if the change is made, make it gradually and monitor closely for significant changes. Change can be bad, but if we never experiment, we are left making more assumptions, but rarely any improvements.

 

[Canuck]

but I think one important part to remember is that if the additional bacteria in the filter media are eating/converting the nutrients, there are potentially less of those nutrients available to the plants.

I just wonder if there are "additional" bacteria in the filter. How much filter media would you have to remove before you limit the population of bacteria? I guess another question is how much ammonia gets sucked directly into the filter how much is pushed around the tank in other water currents before it gets there? I'm a little leary of assumptions too, there are lots of tried and true facts in this hobby that are neither. I think its great if he is going to try this, I'm just treating it as an exercise in logic, and it wouldn't be the first time I was wrong

 

[geofied]

I just wonder if there are "additional" bacteria in the filter. How much filter media would you have to remove before you limit the population of bacteria?

That's a very good point, and I was considering that too. If you believe the bio-media manufacturers, the "special" stuff holds the most bacteria. I'm sure the other media like sponge, floss, etc. do hold their fair share too. For my part I squeeze my filters out under tap water every couple of weeks, full-well knowing that I'm probably destroying some of my bacteria. I guess this is also an option for snickle if/when the bio-media is removed, in order to limit bacteria in the filter.

I guess another question is how much ammonia gets sucked directly into the filter how much is pushed around the tank in other water currents before it gets there?

Another good question. I'm basing my assumptions on my own tanks where the filters pretty much provide the only substantial currents. The only other current generators in my tanks are the fish and me digging around in there. I've noticed a good (or bad) amount of dead spots where things can settle behind driftwood, rocks, bunches of plants, so I know my filters aren't living up to their potential.

I wonder if there is much info out there on how evenly chemicals are distributed in the water column. I would have to imagine water current(s) and tank size, and possibly tank shape would play a role in this. Walstad had some research listed in her book that showed that the root areas of floating plants were home to increased biological activity. Would this mean that I should be taking my water samples from multiple parts of the tank every time? Should a person dose ferts/meds/etc. uniformly in a tank, or are we to assume that there is equillibrium in the water column as chemicals are distributed/distribute themselves?

Oh Plantbrain, where for art thou?:help: I need to subscribe to his newsletter, maybe if I did I would know this by now.

 

[snickle]

Good comments everyone. I agree removing bio-media (unless I remove it all) will not shrink the amount the media can hold, I have tons of bio media, but it should decrease how much bacteria is in the tank at the moment.

My thought is to remove about 75% of the bio-media and carefully track levels.

I am hoping the plants will consume enough of the ammonia and nitrites, that the bacteria will not grow back to full population.

Only testing will tell.

Any advice is welcome.

This test will have to wait a week or two, I wil be ripping out all my substrate this weekend and replacing, so I will need time for the tank to settle out.