Hello, I placed fluorish plant tabs in my aquarium a little over a month ago and now I have found blackish gravel and a sulfer smell. Is this normal?

Please help! Do I need to do anything? Is this harmful to my fish?

Thanks!

There is sulfur in the plant tabs, but I think the smell and the blackish gravel results are from not enough oxygen around the roots. You may want to disturb the gravel in this area to stimulate the flow of water and oxygen there. Charcoal in your filter will remove the smell. Be careful, as too much sulfur can be hazardous to the fish. If you have a gravel vacuum, use it to disturb the gravel at the next water change. This will help remove any escaping gas from the gravel as you aerate it. You might also consider using less of the tabs (break them into smaller pieces) and use them less frequently as well.

Thanks for the quick reply, do you think that I need some sort of emergency water change tonight?

hm. I hesitate to say no, especially when oxygen is in shorter supply during the nightime hours. Try a 25% change as you move the gravel around the areas you mentioned being blackish. You might even get some of the black stuff on the gravel to go up the vac at the same time. I have read where it is similar to the peat that grows in bogs. While this is beneficial to that environment, and plants overall, it seems to be in excess, if you are getting the strong sulfur smell. I imagine the gravel in these areas is not too attractive to look at either. In addition, the peat-like substance tends to lower the pH. You may want to check your pH just for grins, and the level of nitrates as well, just before changing the water. It will be interesting to see how the readings differ, if at all, from what you are accustomed to seeing.

Note: I see I edited my first response at the same time you posted your second. Check to see if I made you miss anything. :)

Well, I haven't noticed a ph change. I have done some reading, and it also seems to match symptoms of anaerobic bateria, but it is strange that it is solely around the tabs. I am having some issues with my tap water, so I am going to test water at my relatives house and possibly get some there. Or, I may go buy some RO water, I'll just have to be careful of the PH. That way, I can vaccum around the area and try to vacuum up the tabs. I did do some extensive water treating on my tap water and I changed water on I think Monday.

thanks!

C.L., any news? How's the tank coming along?