Who Gives A Fish Forums

I've had my mbuna tank up and running for about six months now without any issues. Having a small marine tank means I've always got RO water on hand, which is convenient.

A bit of background info: my tank's 125lt, with an XP3 filter rated at 600ltr. I've got 8 mbuna, all around 2" in size. The pH is 7.8, and I think the GH was around 11 - though I could be wrong. The KH was about 5, give or take.

Prior to using RO water, my nitrates would usually be around 5ppm before a water change. I'd do a 30ltr change every week, using just tap water.

About three weeks ago, I decided to give RO a go and see how it worked out. My first RO water change was 15ltr on the 20th, and since then, my nitrates have been 0. I did another 15ltr RO change last night.

Each time, I've used JBL cichlid salts, and my stats - pH, etc - haven't budged.

So, my question is: how long would you leave it between water changes if nitrates stay at zero? I'm guessing that even with zero nitrates, water changes are still needed, due to the degradation of minerals over time. It's just a matter of how often.

I'd stick to your regular water change routine, just keep adding the JBL cichlid salts as you have been. The salts will help maintain your tank's parameters, and even with zero nitrates, the minerals in the water will still degrade over time, so regular water changes are still necessary to keep things balanced.

I'm a bit skeptical about the zero nitrate readings unless you're using something like a resin to remove them. I'd still recommend doing a water change at least once a week.

When you do a water change, you're not just removing nitrates, you're also taking out other chemicals and hormones that the fish produce. It's essential to get rid of these to keep the water clean.

Don't forget to vacuum the substrate when you remove the water to get rid of as much waste as possible.

I figured as much, so I'll just stick with my weekly 15ltr changes, keeps things straightforward and easy to manage. Thanks for the advice.