What do you keep kh at and WHY?

Elliott Comans · Oct 20, 2019

Im really struggling to understand kh levels and the reasoning behind them.
I understand to high can burn, to low and nothing grows. And I get the importance of stability.
Why run a lps system at 10.5 compared to sps system at 7.5?
Why can you run kh higher in an sps system if your nutrients are high?
Thanks for input. I've been running my lps tank for 2 years happily, got given sps frags and wondering if I need to change my kh from 10 to lower, but I don't like making changes without reasoning behind them.

Bramzor · Oct 20, 2019

Higher KH and Calcium can increase the growth. Side affect is that it uses a lot more so it’s more difficult to keep it stable. There is nothing against running at a KH of 7 for example. There is a nice BRS video about it.

If you are keeping LPS, I see no reason to increase KH and Ca just because you want to add SPS. Even on an SPS dominant tank there might be reasons to go for a lower KH.

madweazl · Oct 20, 2019

I stick to the 7-7.5 dKh range because it's close to what the oceans are at. I've never understood straying from natural levels regardless of reasoning (these corals spent millions of years adapting and evolving in these conditions).

Elliott Comans · Oct 20, 2019

Bramzor said:
Higher KH and Calcium can increase the growth. Side affect is that it uses a lot more so it’s more difficult to keep it stable. There is nothing against running at a KH of 7 for example. There is a nice BRS video about it.

If you are keeping LPS, I see no reason to increase KH and Ca just because you want to add SPS. Even on an SPS dominant tank there might be reasons to go for a lower KH.

So if I've been stable at 10 and only adding few frags I'm all good. What are the reasons to go lower if I end up going sps dominant? I'll go find the be a brs vid now

thanks

Elliott Comans · Oct 20, 2019

Also is it necessary to change salt. Atm I use ultimateaquacare lps which is 10.5kh, should I change to sps salt with 7.7kh?

Cory · Oct 21, 2019

The reasoning is higher dkh demands more growth. If the nutrients arent there, the coral might have problems or get a disease is my understanding.

SeaDweller · Oct 21, 2019

Usually with higher alk and Ca, you need more available nutrients to support the very possible increased growth. But you have less room for error at higher alk levels, you can burn the tips of your sps as the growth outpaces the available nutrients required for growth.

I keep my tank between 7.3-7.6 dKh and my nutrients are low: NO3 1.0 ppm and PO4 0.10 ppm and that’s where my tank does best. When you’re in the lower end of alk, sometimes an uptick isn’t as bad if your alk drifts up. But if you’re at 10.0 and then you’re at 12.0, that spike could be bad.

Also, you don’t want super low/no nutrients. You need to have enough nutrients available. No one person can tell you what that is, you have to literally know your tank and its biology and chemistry pretty intimately.

There’s no right or wrong answer, you just have to choose a starting point and try to maintain the stability that happens at that range. And for this reason, it’s better to start on the lower end, I feel. And lower alk doesn’t mean slower growth btw.