yep, absolutely. fish, corals, bacteria, etc... they all contain resources and need to be included when discussing the total nutrient level of a system. that is what i have been trying to get at all along. give the must have organisms the best shot at the resources they need without competing for resources from decomposition organisms.
Why do you think they are competing? They occupy completely different niches; the benthic organisms serve as an important cog to recycle nutrients so that higher life can use it. This isn't a competition, it's a food web with multiple complementary parts. The main thing that competes with corals, e.g., are other corals, not benthic organisms.
then the time scale is already messed up. if in nature substrates are disturbed regularly, yet we do not do it, then how can an aquarium substrate not fill up faster than a substrate in nature.
The input rate is also way higher in nature, and the net sedimentation rate is vastly higher than in our systems, by virtue of terrigenic input; compared to a coral reef in nature, our organic matter input/sedimentation rate/etc is at least a couple orders of magnitude lower, which is then reflected e.g. in sediment build up rates. Theoretically, if you wanted to replicate natural input rates, then I suppose yes, the sediment would fill up faster. But you'd probably run out of money buying all that food, first.
i am not ignoring the biological role. the biological role is completely dependent on the resources in the substrate. if in nature these resources are washed away on a regular basis along with the benthos, then it has a chance to restart. if in our systems we do not allow for this, then the benthos gets over crowded. what export mechanism does a substrate have for oP?
1) In nature, removal via advection (ie. the sediments being washed away) is a tiny component of the net picture in terms of nutrient removal. The vast, vast, vast majority is recycled in the system, and what does get washed away is replaced by new input. And the benthos itself is not washed away (unless you want to start considering life history and larval migration etc). The types of disturbance that actually do impact the levels of benthic organisms are relatively rare (pretty much just a tropical storm). Much more important is the semi-regular small disturbances such as benthic grazing, larger animals burrowing, etc.
2) The assumption that the benthos gets overcrowded is false. Even if it reached a space-based carrying capacity (which I highly, highly doubt because our abundances are several orders of magnitude lower than on the reef), it would stay at an equilibrium. And we've been over this oP export mechanism over and over...it is remineralized into soluble forms that diffuse out into the water column where it can be either scavenged by other organisms or removed via artificial filtration methods.
how is it removed? what form or another? what organisms are converting the bacterial floc to a form of organic P that is exported from a substrate? we want to know the food chain. it can not be all converted to SRP because the bacteria biomass itself is necessary for the breakdown of the dead and waste organic P into SRP.
It is all eventually broken down into SRP. And then it's removed. Or perhaps the tank has sand bed grazers, which form another removal mechanism. Once at steady state, the net movement is P out of the sediment due to remineraliztion. The fact that you need a benthic population doesn't change this.
that is what i have been trying to say. we have to include all organisms when looking at what the nutrient state of our system is. the more biomass, the more nutrients there are in the system. the more potential for those nutrients to be available if the biomass dies.
it is up to the aquarist to decide how they want to spend their resources in caring for the system. they must know how the various methods work in order to have an informed decision. what the pros and cons are.
I agree, which is why I have been explaining over and over how a functioning benthic sand bed actually works, because it seems benthic ecology is a topic not often discussed in the hobby. What I take issue with are things like the insinuation that because you have more biomass this is necessarily a bad thing, or the incorrect assumption that organic matter or phosphorus will always build up ad infinitum in a sand bed despite well-known export mechanisms.
algae is not able to uptake organic P, organic P must first be converted to SRP by bacteria.
Not true. Although phosphate tends to be the preferred form for uptake, they can utilize both.
in order for organic P to not be building up in a substrate, there must be an equal amount of organic P leaving the substrate.
I think you mean in order for P to buildup. It does not matter what form it is, because it can be rapidly converted between them. There does not need to be an export of organic P for organic P to not buildup; there just needs to be an export of P after it has been converted, and this is precisely what happens (though as a side note: organic P also diffuses out of the sediment after being excreted)
those heterotrophic bacteria that are in the substrate still need to be removed. those in the water column are easily taken care of.
Why? What compelling reason do we have for pulling them out? They serve a very, very important role.
why do you think i haven't? if advective flow or bioturbation did the job that you are saying, then there will not be an increase in waste organic material in a substrates. how would it get in there? what i am suggesting is that bioturbation is actually pushing the waste organic P further down into the substrate. causing a slow migration of P downward into the substrate. allowing more nutrients to be sunk into the substrate.
No, that is not what happens. Bioturbation and irrigation result in a net removal of phosphorus from the substrate. I think I've said this over and over...
sorry, i thought i have been clear that i am not pushing one methodology or another. they each have their advantages. i am just trying to point them out. some methodologies are better for some organisms, than others. all i am saying is that waste organic material sinks, it is going to find the bottom of the tank. you can either hide it in a substrate, or remove it as often as you like when you can see it.
Once again, ORGANIC MATTER IS NOT BEING HIDDEN IN A SUBSTRATE. Period. To say so, especially if being presented as a supposed "con" of the method, is just flat out wrong. It is being decomposed and exported in a variety of different forms. In a mature tank with a healthy sand bed, presumably at steady state, there is no buildup of reactive organic matter in the sediment.
i agree we do over think things sometimes. all i am getting is that there is obviously a build up of material in our systems from the biological functions of the contained organisms. lets just remove it on a regular basis.
If by a buildup, you mean the growth of the organisms in the tank, then yes, there is a buildup by definition. But aside from that, there is no "obvious" build up of material in a healthy tank. And if we do count the growth of the system, so what? You have not made a compelling case for the necessity of limiting biomass aside from the point that there is more stuff to die when you have more stuff.
we know that detritus is accumulating. we can all see this in sumps and when a substrate is disturbed. people recommend siphoning sumps for some reason, but not substrates. not sure why people think that sump detritus is detrimental, but substrate detritus is not. wouldn't you think that any of this material would impact the systems health? whether it is detrimental or not depends on the environment the aquarium owner is wishing to emulate.
This goes back to an old point: we don't know that this detritus is detrimental. We don't know what it is, if it's reactive, etc etc; based on my experience and what I know of the natural ecology of the systems, I honestly think it's non-reactive (possibly refractory, possibly not even organic). I don't remove any and my system is running just fine.
it is the slow migration of nutrients downward through a substrate leaving the upper levels able to bring in more nutrients from the water column. this is how DSB's work, and this is why they "seem" to work so well. Post 228
