I have very low kh and lose pH slowly. Out of the tap my water is 6.8 - 7.0 on average. Needless to say, I have to buff up my water using things ( like Proper pH 7.5, ph Up, etc... ) before I can use the water for my goldfish. I am wanting to swap to using crushed coral in a media bag inside one of my extra slots in my emporer.

I found many suggestions pointing to it's use, but none which detail how to use it. Which brings us to my questions. Hopefully this will help others as well as myself.

1. How much crushed coral should I use?

2. How often does it need to be changed?

3. Do I gradually work up to the suggested amount to begin with?

4. How long will it take for the crushed coral to take effect?

5. Do I use it in the bucket water, and if not, how will I buff up my additive water?

6. Does crushed coral bring any negative effect to the mix that I should be aware of?

Hopefully that is all of my questions, however I am sure as soon as I click post I will think of some more that would be helpful.

Thanks in advance

1. About a handful per 10 gallons.

2. Don't need to change it, it dissolves but that takes months/years. (if in media bag it may get filthy and stinky if not rinsed in tank water regularly, just throw it away and use fresh coral)

3. No

4. It starts working immediately, within a fortnight enough should be dissolved to keep your pH stable.

5. Not in bucket. No need to buffer additive water unless doing large water changes (more than 50%). You could buffer additive water for first fortnight.

6. No negative effects that I'm aware of. Just remember to check water hardness every couple of months as the dissolved calcium keeps accumulating, it may be necessary to do a large water change every now and again to reduce hardness.

Thank you Annette, your answers were spot on. However, I have one more question regarding one of your replies.

About what hardness should I do a large change at?

Ok, a tricky question, lol. Crushed coral adds calcium carbonate to the water so it affects both general hardness (gh) and alkaline hardness (kh). I don't actually test for these, I just test for pH and if that gets above 7.8 (goes very deep blue on the API test kit) I do a minimum 50% water change as this indicates to me that the buffering has built up too high.

In order to be specific you would need both gh and kh test kits. Goldfish prefer moderate hardness in both categories which is 8-12dH (german general hardness) or 140-210ppm gh and 150-300ppm kh. There is plenty of room to move within these parameters so I would try not to let the hardness levels get much higher.

ps. other things that can effect buffering ability are high stocking levels or lots of plants.