Can monthly water changes work?

I keep coming across people (on reddit lol) who suggest that monthly water changes are perfectly fine (and sometimes they even recommend monthly water changes ) if the tank is low stocked and heavily planted. I personally never seen monthly water changes to be good/work. Even in low stocked and heavily planted tanks, I've seen people's fish (specifically bettas) either get sick or get ammonia burns. I just wanted to know, are there any ways someone can make monthly water changes work? Does it depend on tank size (in this post mostly talking about smaller tanks, like 5-10+ gallons)? Really any details about monthly water changes will be helpful. I'm just curious about this.



Some examples of people that said monthly water changes are fine:

First person said they have a 5 gallon tank filled with water wisteria and pothos... but I've seen another person with a 10 gallon, beautifully planted betta tank, and their betta ended up having slight fin rot and really bad ammonia burns.

Second person mentioned he has mostly crayfish and shrimp tanks and that he does a 10% monthly water change in his tanks (and he was also recommending monthly water changes on an uncycled 5 gallon betta tank ) I don't have crayfish or shrimp, so I don't know if that's okay or not.

 

It’s possible but it would have to be done on a large tank (40+ gallons) that’s heavily planted and is very very very understocked. It’s not a good idea though and in most cases it’s probably not going to end well.

 

It’s possible but it would have to be done on a large tank (40+ gallons) that’s heavily planted and is very very very understocked. It’s not a good idea though and in most cases it’s probably not going to end well.

Brings it straight to the points.

 

I have done it on my betta tanks before because life got seriously busy and hectic. Needless to say, the fin rot and just the look of the tank/water made me not do that again.

 

I have done it on my betta tanks before because life got seriously busy and hectic. Needless to say, the fin rot and just the look of the tank/water made me not do that again.

Same here. On my 10g I had to go a month without doing a waterchanges and I started having algae issues because of it.

 

it wouldn't work unless you had very special water.. my water is full of barium (same family as calcium and magnesium) and its toxic to invertebrates. without regular water changes it builds up in my tanks and my shrimp die off from white line as the gh rises

 

I'm not going to say these other posts are wrong. But also I kind of am. Every tank is different. It's all about striking a balanced ecosystem and adding needed minerals back into the water. Some tanks can handle it and some can't. I had a planted tank that was running successfully for years until I recently took it down. I changed water on it maybe 20% twice a year if that.

 

I wouldn't suggest it on a smaller tank, like 29 gallons and below. If you had good filtration and low stocking, with a stable tank, it might work, though I wouldn't put my money that it is better than a normal wc schedule. Just my 2 cents.

 

I keep coming across people (on reddit lol) who suggest that monthly water changes are perfectly fine (and sometimes they even recommend monthly water changes ) if the tank is low stocked and heavily planted. I personally never seen monthly water changes to be good/work. Even in low stocked and heavily planted tanks, I've seen people's fish (specifically bettas) either get sick or get ammonia burns. I just wanted to know, are there any ways someone can make monthly water changes work? Does it depend on tank size (in this post mostly talking about smaller tanks, like 5-10+ gallons)? Really any details about monthly water changes will be helpful. I'm just curious about this.



Some examples of people that said monthly water changes are fine:

First person said they have a 5 gallon tank filled with water wisteria and pothos... but I've seen another person with a 10 gallon, beautifully planted betta tank, and their betta ended up having slight fin rot and really bad ammonia burns.

Second person mentioned he has mostly crayfish and shrimp tanks and that he does a 10% monthly water change in his tanks (and he was also recommending monthly water changes on an uncycled 5 gallon betta tank ) I don't have crayfish or shrimp, so I don't know if that's okay or not.

I have a 155 heavily planted with dirt substrate plus I have lids so very little evaporation with two fx6 filters and I’d say about 100-115 fish and yes I do monthly water changes on that tank driven by the numbers I test bi weekly

 

It’s probably not the best but I do monthly water changes, I get my water tested every 2 weeks and if the jitrates are 40ppm or above I do one anyways. I’ve found that my tank can handle it, even though it is moderately stocked. It also depends on the fish you have, like giant danios and glofish do fine without weekly water changes. I’m probably not the best example, but I am also in high school and have two tanks so it does get a bit hectic.

 

I would like to say that I do monthly water changes successfully, fish can handle the nitrates, I did some aquaculture at tafe and its not something they worry about they don't do all they water changes we hobbyists do. Most fish suitable for aquaculture are hardy to begin with, so I'm not talking about sensitive wild caught rainforest stream fish or something.

Not doing water changes will not mean you have ammonia in the tank either, only nitrate, so that would be false.

 

It’s possible but it would have to be done on a large tank (40+ gallons) that’s heavily planted and is very very very understocked. It’s not a good idea though and in most cases it’s probably not going to end well.

That's exactly what I was thinking. In a big very understocked tank, it might be okay, but with small 5-10 gallon tanks it's definitely risky.

I'm not going to say these other posts are wrong. But also I kind of am. Every tank is different. It's all about striking a balanced ecosystem and adding needed minerals back into the water. Some tanks can handle it and some can't. I had a planted tank that was running successfully for years until I recently took it down. I changed water on it maybe 20% twice a year if that.

I definitely agree. A balanced ecosystem is very important and it will differ for every tank. I'm kind of curious about what was the stocking of your tank?
It would be great if only doing 2 water changes a year was easy lol.

I wouldn't suggest it on a smaller tank, like 29 gallons and below. If you had goon filtration and low stocking, with a stable tank, it might work, though I wouldn't put my money that it is better than a normal wc schedule. Just my 2 cents.

I agree! I'm going to stick to my weekly water changes for now lol.

I would like to say that I do monthly water changes successfully, fish can handle the nitrates, I did some aquaculture at tafe and its not something they worry about they don't do all they water changes we hobbyists do. Most fish suitable for aquaculture are hardy to begin with, so I'm not talking about sensitive wild caught rainforest stream fish or something.

Not doing water changes will not mean you have ammonia in the tank either, only nitrate, so that would be false.

I didn't know the ammonia wouldn't build up. I thought that without water changes the nitrates and ammonia would both rise.

First person said they have a 5 gallon tank filled with water wisteria and pothos... but I've seen another person with a 10 gallon, beautifully planted betta tank, and their betta ended up having slight fin rot and really bad ammonia burns.

The person I was talking about here, said there was ammonia in their tank. I can't remember what the exact number was, but it was very high, so I assumed it was because of the infrequent water changes.

 

maybe its just me but I mess something up and have to do a 100% water change at least once per week

 

maybe its just me but I mess something up and have to do a 100% water change at least once per week

100% ?! I’m assuming that would change up the parameters severely, is there a reason you do them that big?

 

maybe its just me but I mess something up and have to do a 100% water change at least once per week

Doing 100% water changes can crash your cycle. You should never do 100% water changes unless you want to restart your cycle for some reason. Not to mention it’s also really stressful for the fish

Edit: I think I may have misread the post, could you clarify what you meant?

 

There are ways you can do water changes on a monthly basis, but if you want to keep the parameters level there's a ton of chemistry involved. If you have enough natural buffer that the percent of nutrient used is a small percentage of the total, the shift on parameters at a monthly 50% water change is not significant. If you are fertilizing indescriminantly, or have a heavy enough stocking that your plants and bacteria combined are using up more than 50% of your buffer you need to do changes more often.

I see you asked about some details to a tank up there and I'll share some of mine.
I aim for low maintenance, no fertilizer, plant, and cut back plants as nutrient deficiency happens, my tanks look nice but are obviously not instagram worthy planted super scapes. At one time my networked tanks totaling 60 gallons in the system only called for water changes every 6 ish weeks, I would run nitrogen and phosphate deficient with any more changing, and there was plenty of buffer. The stocking at the time: 12 cardinal tetra, 10 harlequin rasbora, and about 20 endler hybrid fish. I added 15 silver tips and the interval came down to about 2.5 weeks. By contrast my little betta tanks and 10 gallons, and various grow outs would all need changes about weekly with the same water, but much less attention to lighting or planting. My current stand alone 29 goes through so much bicarbonate I have to supplement it at least mid week, and due to that it gets weekly changes. It's stocked with a dozen fish from broken schools, 4 otto, a clown pleco, mystery snails, and it is heavily planted (I do not cut the plants back in this one other than trimming for asthetic or shaping).

I would not recommend anyone not having the interest in the chemistry to try to extend changes just for giggles, but it would not surprise me if people that are interested, and likely balancing nutrients with diy fertilizers (where you pick exactly what you want in your tank, and often start with RO water) could easily stretch it, and possibly even find it beneficial. I know many reef folks run a drip that equates to less than 100% per month, and that many research labs purify and remineralize the same water over and over. No one's looking to pay for 1000+ gallons of water to run a tank in los Angeles, so solutions are invented. Personally my water is basically free, but I do the science thing and it works for me.

 

Doing 100% water changes can crash your cycle. You should never do 100% water changes unless you want to restart your cycle for some reason. Not to mention it’s also really stressful for the fish

Edit: I think I may have misread the post, could you clarify what you meant?

You can't crash your cycle doing water changes as the vast majority of bacteria is in your filters not your water, so unless you clean your filters with chlorinated water you should be right.

I tend to do approx. 70% water changes, this is about as large as I can go without air getting into the intake and consequently into my canister.

 

Yup, no issues with 100% water changes. My parameters are so close to tap that it doesn't matter anyways. My fish are happy to have fresh clean water after I mess their home up lol

 

Quick question, is the thread and the thread title assuming that we are including substrate vacuuming as part of the water change? Or is the substrate vacuuming considered separate than the water change? (Vacuum in gravel, vacuum 'dirt' from over sandy surface)

 

You can do no water changes...if the stocking is low enough . But tds will creep up and gH will creep up and eventually you have to do one.

Back when I was a student I've definitely slacked off on water changes for prolonged periods of time....luckily all my fish made it. But then again I had heavy planting and low stocking, for example I had a 75 gal filled with rotala rotundifolia and only about 12 neon tetras. Went for probably a year without water change and just top offs.....

 

Wouldnt a tank with only monthly water changes look awful? I hate how dirty my tanks look when they're due their weekly water changes. Although with that said I'm heavy on stocking so that's probably why.

 

2 weeks max with a properly cycled tank.

 

I'm still learning about the nitrogen cycle and this is now making more sense lol.
I recently stumbled upon another person claiming you don't ever have to do water changes if the tank is heavily planted enough even if it's heavily overstocked. Like people mentioned before, a balanced ecosystem is important, so how would you achieve that? How would you make a "self sustaining" tank?

You can't crash your cycle doing water changes as the vast majority of bacteria is in your filters not your water, so unless you clean your filters with chlorinated water you should be right.

I tend to do approx. 70% water changes, this is about as large as I can go without air getting into the intake and consequently into my canister.

You're right. I just got really used to telling people they should not be doing 100% water changes, replacing their filter every water change, rinsing gravel out, etc.

Quick question, is the thread and the thread title assuming that we are including substrate vacuuming as part of the water change? Or is the substrate vacuuming considered separate than the water change? (Vacuum in gravel, vacuum 'dirt' from over sandy surface)

I consider vacuuming gravel as a part of water changes, but for this thread, I would say just water changes in general.