Water Changes- a bit of the science
Water changes, crucial and debated, but not in my opinion debatable.
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Water Changes, a bit of the Science.
Get half of the water out your tank each week and replace it with fresh. Clean your mechanical media and your substrate. Move your ornaments and décor if you can, get the dirt out of cracks and crevices.
Now we’ve got that out the way let me try and head off the arguments in the comments. Ah who am I kidding, a lot of people stopped reading 29 words ago. I’ll now say this is for freshwater tanks. There is a growing body of evidence that salt water tanks also benefit from water changes, but it’s not as clear cut as it is with fresh water.
The main reasons to do water changes are to reduce some things, and to replenish others. There is now a growing body of evidence that the microbiome will be broader and more stable when there are large water changes. Although this has only been studied in marine aquaria with 90% water changes, and by studied I mean there is a single study.
The things we need to remove are varied. The one we discuss the most are nitrates. I’m not going into a huge amount of detail as that would be a whole book on itself. But the short version. Nitrates are toxic, just not as toxic as ammonia or nitrite.
Nitrates are relatively easy to remove from the water column by using fast growing plants. But they will then use up all the other nutrients in the water column, and you’ll need to dose for them. Now you need to be dosing and monitoring for 3 to 6 nutrients, often more.
Or you could just do a water change. Many aquascapers, even those who barely have any water the plants are that tightly packed in, do large weekly water changes. They also dose a variety of nutrients.
The next thing you need to be removing are the bad bacteria, and fungi, and all the other microorganisms. Warm water is the perfect breeding ground for many of these, by adding clean, recently chlorinated water you have at least diluted the amount of infected water.
I’m not saying this to scare you, well maybe a bit, but in the last decade I’ve seen far too many sick humans, and often it’s traced to a tank that’s only seen top ups for the past few months, or even years. No you’re not going to get all of them out, and if you get a particularly nasty strain 50% won’t keep on top of it. But by taking half the water out, and as much of the organic waste as you can you remove, not only do you remove a good chunk of the nasties themselves, but also their food source.
You will also be removing some of the hormones the fish themselves are producing. Some like the stress hormones are just produced naturally and flushed out the body, others are produced by some fish to impact the growth of others. Some fish produce hormones to aid reproduction, which may not be ideal for a different species in the same tank.
Even plants and algae can produce things you don’t want in your tank. From nitrates, to true toxins, as well as a range of hormones, there are things that even the green things in your tank are producing that you might not want.
But I hear some of you say, they would be producing this in the wild. Yes they would, and most fish in the wild are either in bodies of water that are so large that they are diluted to next to nothing, or, and this is true for most freshwater fish, they are washed away. Even lakes have a large turn over of water. Want proof? Parts of the River Dee are so level that it is officially a linear lake. But the amount of water is so large that a huge chunk of North West England has it direct in their taps, there is a take off for a small hydroelectric scheme, and there is still enough going over to have some fun in a kayak. Trust me I spent many an evening playing in a kayak off that weir. Our tanks are not the wild, and there are a fair number of limitations brought about because of that. We need to put the effort in to correct those limitations, and that means getting out the hose, and replacing some of that water.
You need to also replace somethings, and those are mostly the minerals that are used up by the nitrogen process, by the fish, and the plants, and the bits of algae you’ll never truly get rid of. The big ones are calcium and carbonates, but there are all the trace minerals. Again you can dose for these. But you’ll need careful testing and constant replenishment. Or you could just change the water.
Now there are a host of reasons people will give you for not doing water changes.
Time. You use one pipe to get the water out. I let it run out a window onto the garden, I then attach another hose to a tap and I refill. Or to the pump that is in my water butt that I use for RO.
Cost. In the UK at least it’s pennies, but if you can’t afford to give your animals the care they need, then you shouldn’t have those animals, and that’s a mean thing to say, but I’ll stand by it. At points I’ve done thousands of liters of water changes a week, and it’s not made an ounce of difference. Now the electricity bill from running all those tanks. That was a different matter.
Keeping things stable. In fact not doing water changes causes things to go out of step. As those minerals deplete the pH drops and eventually your cycle crashes. It’s safe whilst the pH is low, but do a water change and it goes back up, and all sorts of issues start. By replenishing things regularly you keep things stable.
Natural. Yeah no, cyanide is natural, avalanches are natural, hippos are natural, none of these I would call healthy. Bull sharks swimming into freshwater, and became psycotic killers that go on homocidial sprees due to the imbalance in the brains, natural, also the inspiration, behind the inspiration for Jaws. Still not nice.
Walsted method. She described me as rude, she might be right, but I don’t agree with her research, and I’ve got the same, or more letters after my name. I might be cheating, my teaching qualification was a weirdly long qualification, and I had to take two qualifications, so more letters. She herself states that fish don’t live as long any more, and with each edition of her book the water changes get closer together. I should publish the McDonald Method, except the golden arches would sue me.
Removing the good bacteria. That’s all in the filtr, so leave your biomedia alone, and all will be fine.
So how do you actually do a water change. You need dechlorinator, that’s it in terms of chemicals unless you are adjusting your tap water. Turn off your filter, heater and anything else. I leave my lights on, but if there is a risk of them falling into the tank, also turn them off.
Stick a longer pipe on your gravel syphon, throw one end out of a window or door if you can, In the shower also works as long as the end of the pipe is at floor level and your tank is a good chunk higer. Start the syphon, as the water is going out clean your substrate, I move the décor, run through the sand, if you have gravel now is the time to really clean out all the organics in there. Wipe the glass to get rid of the algae, and the same for the décor.
Save a bit of the old tank water and clean your filter media. At least half of it.
Once you’ve taken out half, or more, attach a hose to a tap. Be careful not to put hot water back in the tank. Err on the side of caution and make it cooler unless you have an inline thermometer.
If you only have a cold source then fill your tank up in stages, letting the heater bring the water up to temperature between. Make sure the heter is always fully submerged when on. But fish can take a small drop in temperature unless they are super sensitive.
Add dechlorinator to the tank before adding the fresh water.
Angle the hose torads some solid décor, or direct the stream on to a plate.
Once the tank is full disconnect the hose, be careful not to let the end you’re now holding go lower than the waters surface or it will syphon water back out of the tank. Don’t ask me how I know.
It’s done, water changes done for the week. It takes me about 15-20 minutes per tank, and that included messing around with the plants.
