Dark Matter in Substrate ... Cause for Concern?

[whafish]

This has been an invaluable group for me as I have begun my journey as a fishkeeping enthusiast. One issue I've encountered in a small tank I recently cycled (fish in) is a band of dark matter below the surface of my substrate-Seachem Flourite. https://www.seachem.com/flourite.php

This is a small (10g) community tank with Guppies, Guppy fry, Corys, a few shrimp and two mature Mystery Snails. The substrate is about 1.5 inches deep. The tank is cycled with good levels (ammonia/nitrite/nitrate). PH 7.2, Temp 78 F/26c. The fish are all healthy and actively feeding.

What is it and is this something to be concerned about?

[Aiken Drum]

It will be algae. I periodically get a toothbrush and dig it into the substrate and brush it all out onto the surface before vacuuming it out with a water change. A deep gravel vac should achieve the same.

Whether its a good idea or not, im not sure. Ive never caused an issue doing this. Leaving it alone doesn't seem to cause any issues either when i haven't done this for a long time period. It can get get quite thick and heavy if left. I have read that some people cover the front of their tanks upto the substrate line to cut off light and kill off the algae layer with something like a strip of card.

[whafish]

I see. Thank you. This is my first time using this grade and type of substrate. Meant to support plant growth -- it seems all types of plant growth! The earlier rescue tank you @aikendrum advised me on had a river stone substrate and I've not experienced this algae growth in that environment -- so this is good to know.

From your comments, I am concluding that this growth is only occurring around the perimeter of the substrate -- the portion that is exposed to external light. If that is case, your toothbrush solution would seem simple and effective. Thanks there.

I did not mention an unrelated issue I experienced with this tank substrate. Again, working from my experience with the river stone substrate—which I am quite fond of aside from its uselessness for planted growth—I did a basic rinse of the fluorite substrate to remove the accumulated dust from packaging and shipping. After letting it drain through the veggie strainer in the sink. I put it in the tank and proceeded. Upon filling, he water in the tank turned an opaque reddish-pink for several days through multiple water changes. It seems this type of substrate requires extensive rinsing and re-rinsing before use. It is now in a better condition and now what I know to be algae began growing below the surface! Hardly the end of the world, but as a new aquarium keeper, it is all going into the databank. Do let me know if the algae in your experience is just on the perimeter or persists throughout the entire surface of the substrate.

P.S. I am starting another tank next week when it arrives from Waterbox Aquariums (75g). I'll be setting this tank up with a different substrate that seems to get good reviews - Mr. Aqua N-MAR-066 1 L Fine Pet Habitat Water Plant Soil and seeding it with grass seeds from the start. Have you had any experience with this substrate and/or grass seeding that I might keep in mind?

Thanks as always.

WHA

[Aiken Drum]

Yes, the algae layer in the substrate should just be at the perimeter where its exposed to light. Some algae maybe getting into the substrate elsewhere but without light it would die off.

Im a low tech guy. The plants i have are all fine in basic sand and gravel, so i dont have any experience of dirted substrates or growing from seeds. You would be better with a new thread about this specifically. Grasses tend to be more high tech plants, you may need upgraded lighting and CO2 in addition to your dirt substrate to make that work. Ive never had any success with grass in a low tech environment. I have a patch surviving somewhere, but its a sorry piece of grass that somehow hung on after i removed the bulk of it.