Water changes

[AlexT]

An article I did for another forum some years ago may help explain this. It is online on our member @AbbeysDad blog, here:

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Thank you. So, with each water change, you are lowering TDS in the tank? Even if your tap water is very hard, you would still be lowering the TDS because the tank water would have been exposed to many more things that would increase TDS than the baseline (tap water).

Each fish would appear to have a physiology suited to a certain range of TDS such as the example of Amazon / Rift Valley.

TDS shock is a new one on me, and makes sense.

Did you address and I missed it the impact plants have? Fertiliser would increase TDS then? But would this be offset by the plants, or do plants not consume TDS?

Also, did I read it correctly that driftwood and leaf litter can actually reduce TDS rather than (especially leaves) add to TDS levels?

 

[Byron]

Thank you. So, with each water change, you are lowering TDS in the tank? Even if your tap water is very hard, you would still be lowering the TDS because the tank water would have been exposed to many more things that would increase TDS than the baseline (tap water).

Yes.

Each fish would appear to have a physiology suited to a certain range of TDS such as the example of Amazon / Rift Valley.

Yes. The entire environment is what the fish need.

Fertiliser would increase TDS then? But would this be offset by the plants, or do plants not consume TDS?

Yes on any additive increasing TDS. It does mention plants, and they remove some TDS but no where near what can occur.

Yes to the last question, it must have been in one of the references.

 

[10 Tanks]

Hello. I skip all the tedious testing, high end filtration and all the other gizmos and "cut right to the chase". I just change most of the tank water weekly and know that simple duty will eliminate the problem of early fish mortality.

10 Tanks (Now 11)

 

[MuddyWaters]

I have a 15 gallon tank and I typically only go 1 or 2 days without changing at least 2-2.5 gallons. Every other time (or so) I change 4 or 5 gallons. The water condition fluctuations are more drastic in the smaller tank and I'm just better off changing a fair amount of the water regularly. For awhile, I was doing it every day. Now I'm pretty much every other day. NOt sure I need to, but just don't want to find out the hard way. That already happened and it was a mess to work out of.

 

[Sanityassassin]

Can a TDS measurement tell us what is bad TDS and what is not? Can it differentiate? Or is all TDS bad? When I say bad, maybe I mean "less ideal" or "unwanted".

The TDS (total dissolved solids) is a method, similar to the nitrate test in a way, that some hobbyists use to determine their water change schedule.

Unlike the nitrate test, which obviously tests specifically for nitrate, the TDS measures everything. It throws a blanket over the complete mix of waste that's in your water, so no, it won't give you a specific value on just one thing.

There is a correlation between the nitrate test and the TDS test, in as much that they both rise gradually between water changes.

I used to test my TDS after a water change, when it would obviously be at its lowest, I have very soft water. Then it would rise day by day as the waste built up. I discovered that an "X" reading of nitrate, typically, was equivalent, or thereabouts to a "Y" reading in TDS. Once you get a feel for it you can regulate your water changes by TDS alone, some hobbyists I know do just that.

It is worth noting that TDS measures waste on a molecular level, ie, stuff you can't see! As an example, you could have the dirtiest water imaginable, to the eye, and the TDS could be 0ppm! And the cleanest water, to the eye, could be many many hundreds ppm.

Soft clean water is very low in TDS, but hard clean water is very high in TDS. This is due to the dissolved microscopic ions of calcium etc etc, which hard water contains, but soft water doesn't, or to the same degree anyway.

A nice experiment I once did was to dissolve table salt in a cup of clean water, and in another cup throw in a load of dirt out of the garden! One was a muddy mix and the other perfectly clean, but guess which one had an off the scale TDS reading!

 

[Magnum Man]

To clarify this, in the visible dirty water, the visible part is not dissolved, only “suspended” in the water… so that doesn’t read on the TDS meter???
Your mention of the hard water, is why I have never used a tds meter ( we have extremely hard water here )… however, now that I’m using RO water for my tanks, a tds meter might make more sense, particularly when it comes to adding back minerals…

Does a tds meter read the tannins I’m the water from drift wood, or is the tea color mostly suspended solids???

 

[GaryE]

You can test with reagent kits or strips, tds or conductivity. They all show aspects of your water, and they all give useful info. The problem is what info you need. No one method gives you the whole picture. I use my conductivity meter, which I can set for tds as a check on water quality for breeding some fish. For water changes?
I'll argue you do water changes when you have time within a rigid schedule. Every week, but more if you can.
I have the "luxury" of getting soft clean water from my tap. A lot of aquarists come from regions where farming practices result in polluted tap, and a whole subculture within fishkeeping has developed around coping with that. Parts of the midwestern USA and from what I've seen here, parts of England have tap I wouldn't like to drink. If you add areas with too many people and not enough water, there are issues beyond just saying change water regularly, and I respect that even if I don't live it. In my advice, I take clean water for granted. It's really important we start with an understanding of our source water, or we are speaking different languages to each other without realizing it.

 

[Aqua67]

Thank you. So, with each water change, you are lowering TDS in the tank? Even if your tap water is very hard, you would still be lowering the TDS because the tank water would have been exposed to many more things that would increase TDS than the baseline (tap water).

Yes, I use RO water and remineralize it when I do a water change to attain my target TDS. I add water with a TDS around 160 to 180. When I top off evaporation I just add straight RO water.

Did you address and I missed it the impact plants have? Fertiliser would increase TDS then? But would this be offset by the plants, or do plants not consume TDS?

Yes, fertilizer will increase nitrates and TDS in the aquarium. When you have a planted tank you want to have more nitrates than the people with plastic plants or just rocks in their aquariums. Nitrates are food for your plants.

Also, did I read it correctly that driftwood and leaf litter can actually reduce TDS rather than (especially leaves) add to TDS levels?

You may be thinking of pH. Driftwood and litter can slightly reduce pH. To the best of my knowledge, driftwood and leaf litter cannot remove total dissolved solids and minerals from the aquarium, but I would imagine that plants and inhabitants which use some of those minerals in the water could take some TDS out of the water. Keep in mind that tank inhabitants are adding to the TDS all of the time so in the aquarium you will never really see the TDS go down unless you do a water change with water that has less TDS than the tank.

When the TDS in my aquariums get close to 300 in my fish tanks (or 250 in my shrimp tank), that is when I will do a water change using remineralized RO water. Twice a week I dose a liquid fertilizer in my fish aquariums and I do use root tabs every other month or so under my heavy root feeder plants.

 

[Aqua67]

Does a tds meter read the tannins I’m the water from drift wood, or is the tea color mostly suspended solids???

I saw a video experiment where I man tested distilled water, distilled water with crushed argonite that sat for a few days, and a cup of water with tea tannins. The distilled water was next to zero and the distilled water with tea tannins were close to 80. So apparently yes, the tannins do add to the TDS.

 

[Alex Kadyshevich]

There's a very useful ap online called AQ Advisor, which I personally use as my bible.
It tells me I need a 17% water change per week for my 75 g tank with 1 red tailed black shark, 4 red line torpedo barbs, and 2 white cloud mountain minnows

 

[Byron]

There's a very useful ap online called AQ Advisor, which I personally use as my bible.
It tells me I need a 17% water change per week for my 75 g tank with 1 red tailed black shark, 4 red line torpedo barbs, and 2 white cloud mountain minnows

The various serious problem with AQ is that it is unreliable and can function only as the roughest of guides. The programme cannot have all the factors built in to it. For example, feeding...if you feed once a day and only on alternate days, that is a very different situation from someone who feeds twice every day.

The bottom line is, you cannot change too much water, and the more you change the better for the fish. Once a week is usually adequate, but certainly not at 17%.

 

[AlexT]

There's a very useful ap online called AQ Advisor, which I personally use as my bible.
It tells me I need a 17% water change per week for my 75 g tank with 1 red tailed black shark, 4 red line torpedo barbs, and 2 white cloud mountain minnows

That's why I don't use those things. 17% per week is nonsense (not you Alex, the App).

 

[Sanityassassin]

There's a very useful ap online called AQ Advisor, which I personally use as my bible.
It tells me I need a 17% water change per week for my 75 g tank with 1 red tailed black shark, 4 red line torpedo barbs, and 2 white cloud mountain minnows

You've made a mistake in your first sentence, I'll fix it for you, it should read....

"There's a very useless ap online called AQ Advisor."There, that's better.

The best bit of advice you'll ever receive on this forum is, TAKE NO NOTICE WHATSOEVER OF ANYONE WHO TRIES TO TELL YOU HOW MUCH WATER, AND HOW OFTEN, YOU NEED TO CHANGE ON WATER CHANGE DAY. How the hell can they possibly know your system!!!

Only you can decide, by means of getting to grips with your parameters.

 

[Ram419]

It is worth knowing what is actually coming in with your water. But 10ppm is a far cry from 80ppm which is a risk to fish.

So I just tested my tap source water again, which I think I will start making a regular thing I do. Today, there is zero nitrates detected. So perhaps the nitrates from my source vary. I don't know yet if it goes above 10ppm but will find out soon enough if I keep testing it first before using it. I did have some treated tap water store in a container that I didn't use last time I did water changes. I tested that too and it had way high nitrates in it. I went ahead and dumped that water on some plants outside. Does nitrates build up over time when stored in a containter like that? Does if have to have ammonia/nitrates present to build up if so?

 

[Byron]

Does nitrates build up over time when stored in a containter like that?

I don't see how, as nitrate is a product of nitrification so there needs to be an ammonia source, then nitrite, then nitrate. Or organics, which is probably the same process.

Nitrate is commonly from agricultural runoff, when rain washes organics into the water supply whatever it may be. And it can vary with the weather and season. So nitrates may fluctuate. Testing the source water at the start of every water change might be advisable. At least you would know what was going in to the water. If you are on municipal water the authority should give the nitrate range, though that may or may not tell you much more.