Black algae slime growing in sandbed

[Zappy Kiwi]

Hi all bros and sis,

I have experience a situation which makes me ponder. So, I would like to ask for opinion.

I had tired lizard44 method of dosing sugar to reduce nitrate. Works well (my nitrate from 20ppm drops to 0ppm after 7days) , but need to carefully monitor water conditons (esp pH). I refer to the thread http://www.sgreefclub.com/forum/index.php?...6&hl=nnr&st=120

But strangely, on ard the 10th day, black algae slime patches start to appear all of a sudden. Appears after i stopped dosing sugar for a few consecutive days, bcos my nitrate reading remains at zero.

I have attached attached some pics. They are growing close to the water boundary underneath the sand bed. They are growing at several locations (I found 2), so i don't think it is a coincidence. I have stir some of the sand at those location and found that the sand had turned black-grey. Very strange hor?

Just wondering if anyone tired lizard44's method of dosing sugar and experience the same problem.

[Zappy Kiwi]

Picture 1

[Zappy Kiwi]

Picture2.

I refer to those black patches that are visible just underneath the sandbed. Those less than abt 3cm underneath the sand-water boundary. I stirred some sand at these locations and the sand has greyish-black particles. Is this harmful to the tank? Is this part of the side effects of dosing sugar?

I hope someone can share his/her opinion. Thanks in advance.

[blueheaven]

Those are most probably iron sulphide patches

As long as they don't get into your water column then it's ok

Remember, all sulphides are poisonous to organisms

[mUAr_cHEe]

Thats normal to most sand beds? Something about not good waterflow over sand bed.

[Maxstar81]

Poisonous & funky smell too.

Just like the sand at the beach.

BH,

How to remove ah !?

U say ok as long as not in water coloum but

how to remove without getting into the water !?

Won't it leech out sooner or later !?

Sounds like a time bomb to me.

Anyway, had a patch under my rock & i stirred abit.

That tank mainly cardinals from sea so i hack care.

[Zappy Kiwi]

hmm.. sulphide?? But cannot be lah. Cos i never dose any addictives that i do not know of. I have add in kalkwasser (which is Ca(OH)2), sugar (sugar only have carbon chains). I fed my fishes with defroze mysis shrimp. All these doesn't contain suphate,suphide compounds mah.

The water I used to top up the evaporated water is passed thru a polyfilter.

Then where did the suphite came from??

If it is really suphite, how do I stop it from forming in my sandbed?

On a second look at my sandbed, I realize it is not black slime, but the fine sand particles have turned greyish. Some more, the areas where this grey-black sand are found are in areas of high water flow.(motor is blowing the sand diagonally across)

What should i do to the sand? Do nothing or siphon out the greyish sand?

[Zappy Kiwi]

Ok, just did some reading at Google. I think the sulphate can be find in our seasalt mix. And I think blueheaven is most probably right. They could be iron sulphide, meaning they are produced in the sandbed there by the anerobic suphate/suphite reducing bacteria.

But, only my dieing question is, why did it start to grow there? My tank has been up for 2 years and I had worst water conditions and water circulation problems. Did my act of dosing sugar encourage these bacterias to grow (should be manifeast itself) all of a sudden??

Did anyone who dose sugar experience similar problem?