Is it normal to not need water changes?


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Oct 25, 2023
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Western Australia
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Hey reefers I am relatively new to reef keeping about 14 months into my first tank. I recently did not give it the attention it needs and let it sit with no water change for 5 weeks and all I did was feed the fish and my snowflake eel but after kicking myself in the butt and getting a waterchange done and testing all the parameters (before the water change) I was shocked to see it was all very much OK, not great results but clearly ok enough to survive without a catastrophe, I feel very lucky. This thread is not to convince myself or others that proper maintance is not needed but I would like to list the things that changed and the paremeters I had at 5 weeks so that people can discuss their opinions and advice about waiting too long to do water changes or potentially not needing as many water changes as is often said.

Couple of items to note-
The tank is 190L with a 60L sump (50gal and 15gal)
I have a good ATO setup and it always ran replacing about 2-3 litres a day on average.
The fish were fed regularly including an entire prawn (5cm) 2 times a week on average for my snowflake eel.
I had an algae bloom albeit rather small at the begging of the 5 weeks.

Stock list
2 x Ocellaris Clowns
1 x Yellow cloris wrasse
1 x Bi colour blenny
2 x Yellow tail damsel's
1 x Snowflake Eel 30-35cm (13inchs)
5 x hermit crabs (i beleive the eel has decreased this drastically still finding out)
1 x Large rock crab I have not ID'd that came with my first live rock, i should remove him but suprisingly he is yet to cause any issues!

2 x Hammers
2 x Bubble tip anemone's
1 x torch
3 x Zoas
1 x bubble coral
1 x frogspawn
1 x mushroom polyp

After 5 weeks of no water change the only major issue i have noticed is a large increase in the green hair algae bloom. all corals are healthy and fish too.

Parameters after 5 weeks
Ammonia 0ppm
Nitrates 0ppm
dKH 6
Calcium 360 ppm
Phosphate between 0 and 0.25ppm hard to tell

These are not good results by any means but certainly suprised me considering the time frame. Any comments on why I did not lose my tank or if these results are actually really bad and I am miss reading it or any opions on what I did and your stories of something similar please share below! and happy reefing.


likes zoanthids
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Jul 22, 2006
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I've always done water changes every 2-3 weeks. After I retired in 2014 and around my tanks every day, I go about once per month. Before it was more of a safe guard since I could go days without actually paying attention to the tank except at feeding time.


all about the diy!!!!!
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Jan 15, 2010
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Vegas baby!!!!
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We have means and methods nowadays to not change water.. summer time I’ll go 3-4 months without a change because it’s too hot in Vegas to make water and I’m not buying a ac or chiller for my garage to make it haha! It’s easy to hold solid parameters without changing water but you start depleting iodine, potassium, iron etc.. of course these can be replenished also if you wanna buy moonshiners trace elements and send in icp tests all the time… for me it’s easier and cheaper to stay on some what of water change program… I’ll be changing 100 gallons today in my tank as it’s finally cooled down and I wanna make up for not doing them the last couple months. Now that it’s cool I’ll be changing 25 gallons a week on my 300 gal system.

fish farmer

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It is about balance, balance of food and other compounds needed by the inhabitants.

I think of a reef tank as living biomass, from the bacteria, worms, all the way up to the corals. All these living things NEED stuff like food to grow, but also NEED certain water parameters to stay healthy. Feeding, water changes, dosing and the frequency of those inputs are relative to the biomass in the aquarium as well as filtration such as skimmers and such.

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