How Long Without A Water Change ?

Hi,
So I have a fluaval Roma 90 aquarium that's been setup for about a year now. Recently I've been revising and having some exams, as a result I haven't done a water change on my freshwater tank for about 3.5 weeks now, (this doesn't usually happen but it was just as I was so busy) I just tested the water expecting to see ammonia through the roof, but it's fine... In fact everything is fine all the fish look happy the peramiters are perfect, I've done a large water change and cleaned out the filter using tank water. I was just wondering, how long could a tank go without a water change? (Use my tank for an example,20G, 5 L of external filtration 2.5 bio and 2.5 mechanical, with 1 krib, 4 mollies and some BN plecos). Is it possible to do one every, say 6 months and the tank Will be fine? I wouldn't dream of this but I'm just curious .

Thanks,
Ethan

 

In the olden days aka when I was a kid, water change was an annual event. Top ups were done as necessary, but doing serious maintenance was an all day affair.

These days everything from once a week to once a month, depending on local conditions, is the target.

 

It depends on your fish load, how many plants or nitrogen reducers you have, the quality of your water, and if you're dosing anything. The reason I think these are the most important is that the plants will be able to uptake the nitrogen (ammonia, nitrates, nitrites, etc) so a heavily and I mean DENSE JUNGLE OF A TANK may be able to go longer or even forever without a water change. I bring up the quality of the water because some water already has readable levels of nitrogen in it, some water is packed with necessary minerals for the plants and fish.
If you've gone nearly a month without a water change and you have detectable ammonia, I would say water changes are necessary for you. especially if you have multiple BN plecos which have a huge bioload. You didn't mention any plants so I can only assume you don't have any form of nitrogen removal

 

I do a water change every 2 weeks, one tank a week. I do one tank change one week, the other tank the other week.

 

I can never go a week without getting nervous even though its fine, do you have anyone close that could learn and help you out?

 

I would say that if you do regular testing and never see ammonia or nitrites, you would be okay with waiting until the nitrate level goes over 30 before changing out any water. The fewer changes your fish have to acclimate to, the better. I wouldn't worry about a regular schedule unless you don't do water testing. Then monthly 25% changes should be fine.

If you do test and start seeing nitrites or ammonia in a previously cycled tank, then obviously a water change would be in order.

 

Thing is, it's not just about ammonia and nitrites. TDS also build up over time and then when you do a large change, it can be quite a shock to the fish. Unless I'm sick, I usually try to do mine weekly .. sometimes it might get to a week and a half on some tanks (but not my goldfish tank .. that one I do 60-70 percent weekly).

 

Ok, thanks for all the replys,

maggie thecat,
I've never left my tank that long, and wouldn't dare. I usually spend 30 muinet to do the WC, and clean/prime the filters.

Floundering_Around, my tank is fairly heavaly planted with a veriety of floating and in substrate plants, there's also a large piece of driftwood.

@Friar ThomasIII , I have 3 tanks (fresh and salt) I do a water change every Saturday morning (when I get my saltwater from my lfs for my reef)

dwarfpufferlover ,
I've done with the exams now so I'm back on track, my mum is also in to fishkeeping so I may ask her to do it when I'm at school, or I'll try to fit in water changes when I can when revising .

Dch48 I test with every water change, apart from when the tank was cycling the ammonia has never been very high, I have a water change schedule and do them every Saturday along with my reef and goldfish tanks.

Galathiel , never thought about the TDs of the tank , I use RO water in my reef to have a TDs meter, I'll test before and after a water change, next week.


Ethan

 

TDS levels are overdone. You can have readings of up to 2000 with no ill effects. To go somewhat off topic (but not completely), one of the biggest ripoffs that people willingly go along with is bottled water. It is extremely rare to find a place where the tap water is not perfectly fine for usage. Buying bottled water is just a waste of money and I have never done it. As far as TDS levels go, it is not uncommon to find higher levels in bottled water than in the water that comes out of your tap.

 

In my Tap water tanks TDS will decrease about 50ppm/month without intervention. Source TDS is over 2000 though, Brita brings it down to ~800. I go through a Brita a month when I'm not running my aquaponics.
Water change gets done for reasons other than worries about water quality. It really depends on your water.

 

TDS levels are overdone. You can have readings of up to 2000 with no ill effects. To go somewhat off topic (but not completely), one of the biggest ripoffs that people willingly go along with is bottled water. It is extremely rare to find a place where the tap water is not perfectly fine for usage. Buying bottled water is just a waste of money and I have never done it. As far as TDS levels go, it is not uncommon to find higher levels in bottled water than in the water that comes out of your tap.

My tap water is about 350, I haven't tested tap water, the RO water is ment to be 0 but mine is more like 20. Just tested my tank and it's strangely 250, I do occasionally use RO water so that's why it's probably lower than my tap water.

Ethan

 

In my Tap water tanks TDS will decrease about 50ppm/month without intervention. Source TDS is over 2000 though, Brita brings it down to ~800. I go through a Brita a month when I'm not running my aquaponics.
Water change gets done for reasons other than worries about water quality. It really depends on your water.

It seems everyone's TDs is way higher than here in London, I used to use a Brita water filter but it got too time consuming and I eventually gave up.

ethan

 

It seems everyone's TDs is way higher than here in London, I used to use a Brita water filter but it got too time consuming and I eventually gave up.

ethan

Lol, to drink water, it goes through the service filter outside, then through the Brita on the Tap, then through a ZeroWater filter