is overstocking or an old filter causing my ammonia spike

[Lyriqx]

Just did some tests and the results aren't great.

Ammonia's at 0.5ppm, nitrates are about 7ppm, and nitrites are 0.5ppm. I've got 2 clowns, a small copperband, and a mandarin in my 20g tank - could these levels be due to overstocking or the fact the filter's still pretty new (around 7 weeks)? Also, are these levels bad for my leather corals?

I've only just started using RO water - did a 25% water change today and the levels dropped by about half, but still 75% tap water in the tank.

[ravenoak]

yeah i think overstocking could be the main issue here

[zenoxa]

Your stocking level is manageable with regular, generous water changes, but I do foresee a couple of potential issues down the line. The copperband will eventually outgrow your tank, and as for the mandarin, it requires a substantial amount of food, which can be challenging to provide.

As for the leather corals, those levels won't cause immediate harm, but if they persist, damage is likely. I'd recommend increasing the frequency of your water changes for the time being.

[Lyriqx]

Thanks for the advice, I appreciate your input. The fish are still small at the moment, so I've got some time to sort things out. I'm aware the copperband will outgrow the tank eventually, but I'm prepared for that. My mandarin's been doing great since I got it in September 07 - it's been happily munching away on the live rock, which I've got 14kg of in the tank. How often would you recommend I do water changes each month to get these levels under control?

[BoldVoy]

10% weekly water changes are ideal for maintaining stability. I'd be cautious with the RO water transition, as excessive water changes at this point may prolong the mini cycle. Only consider a large water change if the stats worsen; otherwise, it's best to wait it out. Once the time is right, I'd recommend a substantial water change over the course of a week to gradually eliminate as much tap water as possible.