Ode to water changes

Misinformation and opinions about water changes abound. This is not aiming at any of that. I think we all generally agree that water changes primarily work to reduce NO3, the end product of a cycled aquarium.

And, we all know that anything above about 20ppm (and even that has been shown in some studies to impact organ function over time in carp) starts heading into the problematic range.

Water changes work with dilution. But if water changes are to work with dilution, you need big ones - over 50% - to achieve a true limiting effect to your nitrate levels (heavily planted tank folks, of which, nowadays, I am one) I'm not looking at you. You've got other nitrate management systems in place).

What am I on about?

Let's say your aquarium gains 20 ppm nitrates in a week. This is a fairly heavy stocking level, goldfish or an oscar, mbuna or your mother-in-law's guppy tank.

And these are not cruel people, so they do the 30% water change the petshop recommended. Over time, the nitrate build up increases to infinity, though it goes very, very slowly after it peaks at about 67 ppm.

Not great.

In fact, in this scenario, even 50% WC weekly only does so much - maintains it at 40ppm. 70% does better, keeping it under 30%, and 90% (often not very practical, but hey) is just over 20 (22 ppm, to be exact).




If you want to maintain your water at a better level than your weekly increase (which, if this were my 20ppm increasing per week aquarium, I would indeed want to) you'd need to change more than 100% of the water (two 50% changes, as an example, with one done mid week, would keep it at about 12ppm, while two 70% changes stabilises at around 5-ish).

This all falls over if you're not regular, infrequent water changes on a system that increases in nitrates at this sort of rate can lead to HUGE changes in water quality, which can be as much of a problem as high nitrates.

Of course, once you're doing huge regular water changes, your aquarium water will resemble your tap water in all other chemical respects - great if you keep fish that likes the kind of water you have on tap. Awful if you're trying to keep rams or apistos (or anything blackwater) in Johannesburg. And this is probably the other reason why water changes matter - they help maintain all other sorts of water chemistry we don't generally think about too much (unless you are a high tech plant folk, then do continue), micronutrients, total dissolved solids and build up of salts being only some of the picture - WCs keep these stable too.

I know there are many reasons to manage nitrates in ways other than with water changes - but if you do manage it through water changes, do consider two over 50% changes a week. Keeps things very stable, nitrates low, and fishies happy.

 

Nice post.

Ive often wondered why its not more commonplace to do bigger water changes as the laws of dilution make the frequent small water changes ineffective. Lots of people do multiple small water changes some even multiple times a week thinking they are being good for the fish but at the end of the day they are just creating work and negatively affecting the fish.
Personally what works for me is to stagger the water changes each week. So I do a 10%(weekend 1), 20%(weekend 2), 30%(weekend 3), 70-80%(weekend 4) that way I get a few easy changes and then one big one per month. It of course depends a lot on your tank setup as you stated so a cichlid tank needs a heavier change than that nice planted shrimp tank.

 

We are so lucky here in Cape Town, perfect water for soft water fishes. My tap is spitting 52ppm right now, in the heart of winter it goes down to below 30ppm. Easiest way for me to determine wc's is to monitor conductivity and compare to my incoming water. Don't need to fiddle with tests, thank Poseidon.

 

Yes, TDS pen.

 

They are around R180-R220 depending on where you buy. We tested a few against an expensive Hanna unit and they where good. The one I use now is 2ppm out from the expensive unit and the worst was 4ppm out.

 

No haha, I was thanking the god of the ocean because it's so easy and quick compared to liquid testing.

The new one is called TDS-3 by HM Digital but most that we find here has no branding. My one is called TDS-2 but no branding. Just ask the shop to test it with a calibration solution before you buy to check that you are happy with the accuracy. a Few ppm out is negligible. It just measures conductivity, compensates for temp and converts it to ppm, a very simple device.

Ask for a quote from spray tech if you don't want a cheapy, they are situated next to Tigervalley mall and stock a wide variety of quality equipment.

Just for interest sake, pH meters are a different story, the affordable pens on the market unfortunately don't give accurate readings in our soft water so you have to go with a lab quality probe to get a decent reading.

 

Interesting read

Thank you. The issue I have with 2 50% water changes a week is surely that will shock the fish if your nitrates are high alreday and also that will take a while to do

 

i have often said that i hide my poor fish keeping skill behind huge water changes, got used to it keeping large cichlids and now with stingrays there is just no way around not doing atleat 1 50% a week, ideally 1x50% and 1x37.5% is my happy spot.
my major issue is in winter 50-60% water changes with cold water never fun, but have a work around with hosepipe in shower.
@BoelderBeestie thanks going to try figure out new use for tds pen, jhb hard water doubt it will be as easy my side thou

 

Can't you mix hot and cold water in winter to help?

 

I have the same problem, it's the cost of heating large amounts of water that gets you. With sensitive species it's unwise to use a geyser.

 

It will work fine, do your big wc and measure the tds. Then again right before the next wc. Compare the readings to your incoming water. You will have a good indication if you are doing enough wc's.

 

Thank you. I learnt something new today

 

using water from geyser can result in more heavy metals in your water, and is bad for fish. Most good water conditioners should have a heavy metal removing properties, but there is always risk.
One thing to mention on water test, is to check your tap water as well, have had a few nasty surprises with terrible water being supplied. This normally happens in drier months.

 

I didn't think of this. I usually use water from my geyser because it's cooler than tap water. In my case sometimes 40degrees celcius from the cold tap. Geyser is never switched on as that is my spare bathroom used only for fish related activity

 

I'd be a little careful with this with hard water with a high dissolved solids - I don't think you're pick up any kind of difference, at least, not on a significant scale, but you could still be quite overdue for a water change. Especially in winter I find my TDs goes into just about the 600 range, and at that scale, 10 or 20 ppm NO3 won't look particularly significant. This works better with soft water!

 

@top dog , yes way to risky. My geyser broke last year, man you should have seen what came out of that thing.