Sulfur Smell in 1 year old tank

[Marnol D]

Hello,

I have had a 50 Gallon tank setup for over a year now. The last two times i have gravel vacuumed the tank the water coming out of the tank smells of sulfur(edit: this has been probably over a month that the smell has been there when gravel vaccing). What causes this and is it anything i should be worried about? Mulm is present around the root plants ( i dont vacuum these areas)

Substrate is black gravel. (tanks does have 17 small mystery snails but all are alive and moving so i dont think its dead snail)

ammonia 0

nitrite 0 

nitrate 10~ ( running CO2 and have to dose ferts to keep nitrates readable)

ph 7.2

sponge filter is the filter and sponge was cleaned 3 weeks ago. 

 

Edited November 11, 2020 by Marnol D

[MickS77]

Could be a cyanobacteria outbreak coming.

[Marnol D]

@MickS77

 

Should i take the preemptive strike and dose erythromycin? Im also not running a power head at the top of the tank do you think this would add movement near the substrate to keep water moving? (currently have a rainbowshark as the bottom fish so he doesnt move substrate really or anything) 

[Aubrey]

Hydrogen sulfide gas from build up of decaying matter in the substrate smells like sulphur.

[Marnol D]

@Aubrey

I was thinking i may be that and i just keep hitting pockets of it when i gravel vac. Is there any danger to the fish? And would more gravel vaccing eliminate it.