[pyrrolin]

I have in the past had the view that as long as nitrates are low, water changes aren't needed and only top ups need to be done and just doing a bit of a water change every couple months is fine.

I have changed my view. I had not done any water changes in quite some time and did some larger ones, nitrates finally went up. I have dirted tanks so that might be the main issue and I have driftwood. My tanks seem to get darker after a while, even though the levels are all good. A large water change made my tanks much clearer.

So there was stuff in the water making it darker, probably mostly tannins. I see a few problems with this, first is the look of the tank, just looks nicer with clearer water. Second is the stuff making the water dark is probably not great for the fish, tannins are usually fine, but who knows what else is in it. And the third thing is if the water is darker, light can not penetrate as well for plants.

Regular water changes help keep things looking nicer at the very least.

 

[bob123]

I would say that it depends on the fish in the tank. The tank I keep my wild caught Altums in I add black water extract to get that dark look plus I have driftwood as well. My other tanks are kept clear as the fish in those tanks do not require that dark water look. I do water changes every week on 21 tanks.

 

[SKurj]

A lot of the trace elements etc will also be depleted over time, and just top ups may not be enough. I have also noticed that fish grow faster with more water changes.

 

[Fishfur]

I think more water changes are better than fewer, for the reason Skurj gave. Over time, minerals and micro elements do get used up, especially in planted tanks, and ferts only replace a select few of them most of the time. I think both fish and plants benefit from more frequent changes, regardless of nitrate levels.

 

[Lee_D]

All my tanks are planted. I used to do water changes only on occasion but a while back I decided to do them weekly. I think the water changes add good nutrients as well as removes bad ones.

Lee

 

[solarz]

Actually, if we're talking about soft-water tetras, their native habitat is dark water with practically no mineral content.

There's also no evidence that water changes would add more minerals to the water than top ups. Logically, water changes would balance the mineral content of your tank toward the mineral content of your water source.

If you do only top ups, you are more likely to get harder water as I'm pretty sure water evaporates much more quickly than minerals get uptaken. That's assuming you top up with tap and not RO, of course.

Water change also makes the assumption that water out of our tap is better than water that has been aged in the tank. While I don't think it makes much difference to the fish, that is not an assumption we can make without evidence.

 

[Fishfur]

Can't argue with that Solarz. It's only logic, topups alone do increase the TDS readings. I've got a TDS meter and it shows this clearly. Water changes reduce TDS, because you're taking out some of the build up and replacing it, not simply adding more.
If reef keepers always topped up with more salt water, their fish would be living in a brine so strong they'd be pickled !, and while it's perhaps not quite as critical for fresh water, the principle is the same.

Happens I heard a very interesting tidbit about ammonia in our local tap water. We know it combines with chlorine to produce chloramines, and they do disinfect longer than chlorine alone, but that's apparently not the main reason they are there.

A friend of mine typed up a research paper for a university grad, on the topic of the purpose of ammonia in treating Lake Ontario water. Needless to say, she could hardly type it without also reading what it said.

What ammonia does, according to this paper, is bind dioxin and one other extremely toxic chemical, sorry, the name just escapes me at the moment. And because the lake water is pretty thoroughly contaminated with these chemicals, ammonia is what they're using to bind up these two particular toxins, so the water will be 'safe' to drink. She started using all bottled water after she typed up this paper, btw.

 

[pyrrolin]

I remember way back in the early 80's as a kid and hearing about the pollution in lake Ontario. I am not sure if it is better or worse 30 years later

 

[SKurj]

If reef keepers always topped up with more salt water, their fish would be living in a brine so strong they'd be pickled !, and while it's perhaps not quite as critical for fresh water, the principle is the same.

But.. reef keepers still need to change water.. reef keepers need to dose and change water to keep elements in check or livestock die. In a reef the animals do consume the elements, just like in fw. Evaporation doesn't consume the elements, but the livestock sure do.

 

[zenins]

I remember way back in the early 80's as a kid and hearing about the pollution in lake Ontario. I am not sure if it is better or worse 30 years later

There have been occasions in the the last few years when long distance swimmers from Niagara-on-the-Lake have encountered pollution on their way to Toronto and had to come out of the water

 

[ksimdjembe]

There is definitely an increase in the amount of 'cleaner' water in the great lakes as opposed to 20 or 30 years ago.
It's not to say it's perfect at all, but it's much better than it was.
The other thing about big lakes like Ontario and others is that the proximity to city centers, or water treatment locations plays a pretty big role as well. Water is the great diluter. I'd not want to swim out of Toronto harbour, but sandbanks prov park is beautiful.

 

[Fishfur]

I think that's more or less what I said concerning reef keepers.. they have to do water changes, topping up alone won't work. I did refer mainly to the salt buildup, but of course minerals are consumed as well.

If you think about it, livestock like fish have to be consuming minerals from their water, no matter if it is fresh or salt, because they use them as part of their osmoregulatory processes. That's a big reason why you can't keep fish in pure distilled or RO water. Neither has any mineral salts for them to use to keep their internal fluids and salts balanced.