Black gunk forming in my substrate, what is this?

[timuraydin]

Hi,

I have a 35 gallon planted tank. Currently there is java fern, a few crypts and a ludwigia. The tank has 4x18W fluorescent lighting, a large canister filter, and CO2 cylinder. I was using estimative index in this tank, but for the last year, the tank got neglected. The problem I am talking about now did exist all the time, though. Below are the pictures. As can be seen, the substrate is infested with some type of algae (as far as I can tell, at least ...) The grabel thickness is about 8 cm and consists of coarse sand. Can anybody tell me what the problem is?

 

[dutchy]

It's BGA, Blue Green Algae. Take some tape and cover it, so it doesn't get light. In most tanks the substrate goes up sloped front to back. That way you don't need a thick layer like you have now. It looks better and prevents BGA.

So of course you can remove some of the substrate in the front until it's almost flush with the tank's rim.

regards,
dutchy

 

[timuraydin]

Thanks for the response. Is the BGA only at the point where the glass and the gravel meet, or does the whole tank have a BGA problem? Did the BGA occur because of the thick gravel?

Just an additional info: For some months in the past, gas was escaping from the gravel as a large bubble every now and then. Nowadays I don't see that anymore. When I un-rooted a crypt in the past, I noticed that the roots of the crypt were enormous. It almost extended all over the tank bottom!

 

[dutchy]

It's only where the gravel meets the glass, and doesn't mean your whole tani has a BGA problem. Plants bring O2 into the substrate, sometimes it escapes. It doens't necessarily mean anything is wrong here.

The BGA just occurs because of the thick gravel and light. I'd take out a big part of it at the front. Don't forget to change like 75% of the water and to dose afterwards.

 

[anda]

Don't worry about it too much. I have it and have to live with it. My tank is visible from three sides so I can't realistically slope the gravel... I never had issues with it.