Water change question

[Saltfishlover]

I have a coral tank and fish only tank. My coral tank has been low nutrients and I've been trying to bring up nitrate and phosphates. They current sit at .01 phosphates and 00 nitrates. Thr take is 2 years old. Its been a while since I've been able to do a water change due to fear of making things worse with low nutrients.
My question is, can I use the fish only water after changing it, and add that to my coral tank? Would the fish only tank have depleted trace and alk somehow making things worse?

 

[tzabor10]

Try feeding more
Yes, I have heard of some reefers trying to recycle water successfully. But few keep at it long term.
Good luck

 

[Uncle99]

Fish add to coral nutrition via excrement into the water so that could work, however anything “in” the fish only tank (a pest for example) could inadvertently be added to your coral tank as well unless that water is well filtered.

It’s easier IMM just to dose up nitrate to 5ppm and say phosphate 0.1 or so and use feeding increases for long term maintenance of those target suggested values.

 

[Fish Fan]

As mentioned, feeding more will help to raise N&P, and the coral food Reef Roids is good at brining up phosphate specifically.

You could also dose food grade sodium phosphate for the P.

And many are now dosing ammonia to keep nitrate up. Here's a could posts from RHF on ammonia for more information:
https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087/
https://www.reef2reef.com/ams/ammonia-is-our-friend.1062/