What's the point of water changes, really!?

[aqua_chem]

While I agree with the observation that the plant mass has sequestered the nitrogen from interacting with (and therefore harming) much of anything, it has in fact not been removed from the system. The same amount of nitrogen is present in the system, although in a different form. As plants grow and you remove those plants to sell or trade, then you have effectively removed the nitrogen from the system.

The best method for preventing this reservior from being an issue is to monitor your tank on a regular basis ~ as Billbug pointed out, most people don't allow a large dead plant mass to simply sit in the tank and decompose. But what happens when you are away on vacation or you simply get busy and don't pay enough attention to the tank?

I think we're arguing semantics about the definition of a 'system'. Technically, the system would include everything between the glass of the tank, but I was considering to be essentially 'everything in the water' because, as you pointed out, short of catastrophic failure the nitrogen is an unalterable state. If you're considering what effects water changes have on a tank, then the nitrogen sequestered by plants isn't really relevant.

 

[Fresh2o]

Some of my hobby research over the past couple of years has been into the existence of similar anaerobic bacteria within the freshwater environment. If they can be used successfully on the saltwater side of things, they should also be able to be used on the freshwater ~ but that is a whole other discussion in and of itself.

Yes, that would be a discussion in and of itself and I would definitely follow it. I have often wondered if the equivalent of LR and deep sand beds can be applied to the FW environment. Of course I believe this only addresses nitrogenous compounds.

 

[jetajockey]

There's a good bit of info on freshwater dsb by hobbyists if you dig a bit, its pretty interesting for sure.

 

[Mebbid]

Wow, soo many things to respond to, I was going to take time to quote them all but.. good lord

Jeta - Your hormone statement is 100% correct. I've seen this happen myself. My room mate and I both had 10g tanks with guppy fry. I was doing daily 20% water changes while she was doing a weekly 30 - 50% change. Being fed approximately the same amount of food for the tanks my fry grew WAY faster than hers. In fact I still have a fair number of them and they are as of now an adult size and are breeding themselves. Her guppies are approx the same age give or take a week and are easily half the size of mine. Adding onto that she put some in a HOB breeder box on her 29g tank and those guppies started growing a lot faster than the other despite having a smaller swimming space.

Alkalinity: I am surprised nobody has mentioned this yet. It's a bigger issue in salt water tanks than fresh I suppose. Bacteria utilize alkalinity when they grow. We see this when the tanks are going through a fishless cycle causing a pH drop. Saltwater tanks usually have additives put in the water to increase it which dramatically help with the issues of few water changes.

Nitrate: I see the point of brought up a few times in regards to plants and algae which makes a lot of sense. But I see the tanks rapidly being depleted of the nutrients for the plants to grow fast enough to utilize enough nitrates. Given a lightly stocked tank live rock should be able to be used to create nitrate reduction in fresh water much the same way it can be used in salt water. However, if I'm not mistaken the nitrate consumed by anaerobic bacteria gets utilized for the oxygen component of it and then released as nitrogen gas which then leaves the aquarium. It shouldn't get "stored"

There are probably half a dozen other things that I am missing to comment on but *shrug*

 

[Wy Renegade]

I think we're arguing semantics about the definition of a 'system'. Technically, the system would include everything between the glass of the tank, but I was considering to be essentially 'everything in the water' because, as you pointed out, short of catastrophic failure the nitrogen is an unalterable state. If you're considering what effects water changes have on a tank, then the nitrogen sequestered by plants isn't really relevant.

I don't consider what we were doing arguing, but rather clarifying through discussion .

Nitrate: I see the point of brought up a few times in regards to plants and algae which makes a lot of sense. But I see the tanks rapidly being depleted of the nutrients for the plants to grow fast enough to utilize enough nitrates. Given a lightly stocked tank live rock should be able to be used to create nitrate reduction in fresh water much the same way it can be used in salt water. However, if I'm not mistaken the nitrate consumed by anaerobic bacteria gets utilized for the oxygen component of it and then released as nitrogen gas which then leaves the aquarium. It shouldn't get "stored"

Quite correct ~ as I pointed out, it is gassed off.

 

[dwayne.aycock]

I have the information aquachem is referencing. Though I can't find it in relation to fish, some literature exists in reference to dialysis patients. It goes something like this: water in the body is the transport system for the supply of nutirents to the removal of toxins. The liver and kidneys are filters. The bladder is a resevoir for toxic and dead wastes as a biproduct of substances and foods ingested as well as the removal of dead blood cells. In the dialysis process, the blood is filtered with water and toxins are held in suspension and filtered. Charcoal is used here and absorbs mass of a certain size. The aquarium filters, biological activity and waste produced functions in a similar method. There is a buildup of hundreds of proteins, acids, salts, dead organisms (visible and microscopic), ammonia, heavy metals, organophosphates, etc contribute to TDS which MUST be physically removed. If not removed, these substances build up in the tissues of the fish. Some have a rather benign effect (stored) while others are much more toxic and observable.
D