How often do you change the water in your fish tank?

I have a tank that's approximately 290 litres (75 gallons), and I do weekly water changes of about 40%, sometimes just under 50%. It is heavily stocked with lots of small schooling fish, 55 of them. I do large water changes for this tank because the Dwarf Neon Rainbows and Panda Cories I have do better with more water changed per week than most fish.

Then I have a 40 litre (10 gallons) with a colony of Cherry Shrimp. I still do weekly water changes, but I change a much smaller amount - only 15% to 20% at a time. With this, I do a small amount because invertebrates have more trouble acclimating to new water and go into shock more easily, and also because it is very lightly stocked. In a tank with fish, I wouldn't ever do less than 25%.

Then I have another 40 litre (10 gallons) with a Betta. I still do weekly, but usually do about 40% - I would do less, but if I change 40% I can add an even capful of Excel for the plants rather than having to measure smaller doses. Just easier for the fertilizing regime. If I didn't have to worry about that, I would probably do 25% water changes since it is lightly stocked with fish.

Frequent smaller ones are always better, in my opinion. It would probably be ideal for me to split my 290 litre into smaller water changes twice a week, but it is so involved with that much water, and the sink is on a separate floor, that's why I just do one large weekly one. I've noticed that my sensitive Panda Cories will actually start to become less active if I ever go as far as 3 weeks between water changes, and are most active and breed more if I make sure to do them weekly, so I think weekly is important. Also, on most aquarium books and magazines people suggest doing water changes weekly. I think as far as the amount changed, assuming you are doing fish you could do 25-50%, with 25% for lightly stocked tanks and 50% for heavily stocked ones with fish that need larger water changes. If you have a fish like that, you'll find a lot of care sheets will mention that they need that specifically. If you have fish that don't care either way and your tank is average stocking, I think your 30% is a good one to go by, although I would up it to 30% once a week, especially if you ever decide to get more sensitive fish. You never want to do more than 50%, because if there is a big parameter change or a temperature difference the fish can go into shock if you change more than 50% at once.

Every Saturday

30%

130 litres

30 small fish

Rebuild every 6 months, but do not interrupt the cycle, just change out substrate and rocks

Smaller, more frequent changes are a lot better than a large change every now and then.

i have a 55 gallon tank I only take half of the water out 2 times a week then I replace it with clean fresh water making sure I add some stress coat, salt ,and to make the water tap safe. I have around 10 fishes mostly goldfishes 1 pleco 2 eels and 2 Cory fish good luck :)

My tanks are done weekly

2 Breeder tanks of 40 gallons 25% weekly

1 47 Gallon 25% weekly

1 55 Gallon 25% weekly

125 gallon i change either 25% or 50% weekly as it houses an Oscar

180 Gallon Reef tank .I top off with RO water every couple of days but usually its 25% weekly .

300 Gallon this is the only tank that has 2 .25% weekly water changes

I have a 5 gallon tank and I do a 30% water change every Sunday. Right now it has 2 goldfish and 2 rosy red minnows.

I have a much smaller tank with only 4 fish, probably around 10ltr, and I change the water in it just once a month.. Obviously it's a lot more difficult to clean out your own, you should probably do a 100% water change sometimes so that contaminants aren't building up in the lower half of the tank. I'd say larger less frequent when dealing with a tank of your size, c.-6 weeks

I have kept fish for years, doing weekly 25% water changes and a monthly 40-45% water change. I have had tanks ranging from 2.6 gallons to 75 gallons. Currently I have one 2.6 gallon and a 6.6 gallon aquarium and they are doing just fine.

Your tank is seriously over stocked for that size. I keep around half that in a 180ltr and do a 20-25% water change once a week

I have a 10 gallon with 1 betta in it, and 3 baby clown loaches that are growing out for my husbands planted tank. Eventually it will be just the betta and possibly a ghost shrimp or two.

I kept tropical fish for years & I very rarely changed the water, I just used a good filtration system to keep things running. If you are using tap water make sure that you are adding de-chlorination solution as the chemicals in the water can kill the fish if untreated. Also be careful not to cause large deviations in the water temperature as this can weaken them & make them susceptible to infection.