FISH ONLY - Any reason to do water changes?

[jjencek]

I have a fish breeding setup of 10 tanks (700 L total). The sump filtration is able to keep ammonia (0), nitrite(0), nitrate(0), and phosphate(under 0.2) at decent levels. If these values are fine, is there any reason to do water changes?

I have an SPS tank where I do 10% WC every ten days or so to keep up with elements I don't measure, but does a fish only tank need that?

 

[Jay Hemdal Verified Community Expert]

I have a fish breeding setup of 10 tanks (700 L total). The sump filtration is able to keep ammonia (0), nitrite(0), nitrate(0), and phosphate(under 0.2) at decent levels. If these values are fine, is there any reason to do water changes?

I have an SPS tank where I do 10% WC every ten days or so to keep up with elements I don't measure, but does a fish only tank need that?

I would still perform regular water changes. Fish don't really absorb micronutrients or trace elements from the water, but other changes occur in "old water" that really need to be diluted through water changes; organic acids can depress the pH over time for example.

The trick is that this system could probably go quite a long time before any apparent need for water changes appear. I mean, possibly years. That would give you a false sense that water changes aren't required. However, the lack of water changes is additive, and eventually it will reach a point where they will be required.

What system are you using for denitrification? Without an active system, I would expect that the nitrate would eventually climb. I prefer to keep fish breeding systems below 20 ppm nitrate-nitrogen.

Jay

 

[Little c big D]

I'm suprised you have no nitrates. I agree with the occasional water changes.

 

[jjencek]

I'm suprised you have no nitrates. I agree with the occasional water changes.

I use RedSea NoPox that might be doing that.

 

[jjencek]

I would still perform regular water changes. Fish don't really absorb micronutrients or trace elements from the water, but other changes occur in "old water" that really need to be diluted through water changes; organic acids can depress the pH over time for example.

The trick is that this system could probably go quite a long time before any apparent need for water changes appear. I mean, possibly years. That would give you a false sense that water changes aren't required. However, the lack of water changes is additive, and eventually it will reach a point where they will be required.

What system are you using for denitrification? Without an active system, I would expect that the nitrate would eventually climb. I prefer to keep fish breeding systems below 20 ppm nitrate-nitrogen.

Jay

I have a sump with 50 liters of filtration media, oversized skimmer, and I feed bacteria with NoPox. I am also thinking about adding an algae scrubber and clarisea filtration. I vacuum the tanks through a 200 micrometer sock every 3-4 days.