What are the water change requirements of a 20 gallon tank? I thought it was 20% once a week, however my mom?

Depends how many fish you have.

If the tank is overstocked you may need to change 50% -twice a week.

If the tank only has a few fish you can do much less.

25% every three months sounds nowhere near enough. Long term the tank will suffer from nitrate buildup which slowly poisons your fish. So it may work OK for 6 or 12 months, then the fish start dieing for no obvious reason.

To be sure - test the water for nitrate buildup. If the level starts getting high, you need to change more water.

20% every week is a sensible schedule, if you change more then you need to, it does no harm.

Ian

The rule of thumb use to be %20 a month. That has changed some what.

The best way to know how much water to change is by the tanks water parameters and how the the livestock are doing. In other words 3 months may be fine if all the fish are fat and healthy and the ammonia, nitrite and nitrate are low. Evaporation does not remove anything but water. No salt ammonia nitrite or nitrate is removed via evaporation.

A water change is used to lower the percentage of bad elements in the water. IN a reef tank they are also used to replace trace elements. Trace elements are not really a concern in a fresh water tank.

During the 3 months start checking after 2 months things like ammonia nitrite and nitrate levels, also test the ph and alkalinity of tank. If alkalinity, and or ph is low the 3 months is too long between water changes.

I have a 20 gallon and to keep it clean I do about a 25% water change every two weeks. It really depends on how many fish you have, the more you have the more you have to change it. I have 5 balloon mollies so every couple of weeks is enough. If you have more (like 10), I would do a 25% every week. 3 months is a really long time to go without water changes, even if it is a little bit of a bigger tank.

Depen on

1.How many fishes and size

2. Size of the Tank

3. The filter system

Exp: 55 Gals tank with only 1 Gold fish 8 in's in it and running 2 Fluval FX5 Canister Filter( Filtering 925 Gph x2) i am sure he/she/it can get by without water change for 2-3 months!!

Just a exp to give u some ideas why these 3 are matters for how offens u u do all the cleaning for ur fishes.

Hope it helps and good luck!

i would keep up with 20 % a week. It is a good amount. It is enough for where your fish will still be healthy but will not require too much effort for your part. For your mom, if she has a fewer fish then she might not have to do as many water changes but 3 months is pushing it, i personally would not go for more than 2 weeks, 3 at the absolute most for any of my tanks, but most of my tanks are fully stocked and some have messier fish like my cichlids

let see 10% of 20 is 2 gallons half of 2 is 1 so 2 and 2 is 3 but that is 15% so 3 + another 10% 2 equals 5 gallons leave you mom alone

Well for most fish tanks and for all tanks the actual requirements are around 10-15% weekly to bi-weekly but also if you have to depending on how many fish you have in the tank and how big they are you will need to do about a 20%water change weekly or bi-weekly pertaining what I said above as well.So its more of how many fish you have and how big they are as well then you will need to do what is for the accomdating fish and the tank

i think 20-25 % a week

it is 10%.