Soil cap - sand or pea gravel?

[OttawaFolkFestivum]

Hi all,

I'm preparing a soil tank and debating what cap material. I'm leaning towards pea gravel as I had success with HC plant growing well in it. I also would like to keep pH lowered.

I understand sand can also look dirty.

I picked up some bags of play sand from Home Depot but I'm thinking of getting some pea gravel from Canadian Tire.

What do you prefer? 

[Gilbotron]

I've tried a bunch of different materials and here are my findings...

Pea Gravel: Because of larger grain size, tannins tend to get in the water column more readily so water will go tea coloured very quickly. Great if you want a black water tank, but also totally manageable with either carbon or Purigen in the filter (or a lot of patience of course). If dirt does get pulled up (uprooting plants), it tends to go away on its own by falling back between the gravel.
Grit Gravel (smaller than pea, larger than sand): Personal favorite. Looks natural, and grain size small enough that tannins don't leech into water as quickly, and uprooted dirt falls back between the cracks so doesn't leave the tank looking dirty.
Sand: Very little tannins get into water column, but any uprooted dirt will settle on top leaving a mess. Needs to be vacuumed on occasion to keep clean looking if sand is white - play sand the dirt looks nice and natural.  Another big drawback of sand is a lot of flow (or waving your hand) can make a huge mess by blowing the sand all over and exposing the dirt. Its a lot more fragile to maintain the cap vs gravel.
Black Coal Slag: Very similar to sand, except the extra nutrients will cause algae outbreaks if it isn't very heavily planted (90% + floaters). Because its black, any uprooted dirt hardly noticeable so doesn't need vacuuming, and I find it isn't as susceptible to getting blown around like aquarium sand is.

I haven't tried Pool Filter sand, but I've heard/seen good things. I intend to try that next...

Recommendation: If you are looking for no maintenance and intend to fire and forget - sand looks great.  If you can't leave things alone and are going to be making plant adjustments, gravel/grit is more forgiving, but you will need to add some purigen or charcoal to the filter if you don't want dark water. 

Can't really speak to pH of each as I don't usually test my water but the cap shouldn't affect it given they are all inert. If I had to speculate then I would think sand would take longer to lower the pH given less soil is coming into contact with the water (more tightly packed), and based on what I've seen with how quickly the water turns to tea with a larger sized grit.

Hope this helps!

[OttawaFolkFestivum]

Thanks Mike - I realize it's an age old question...I'll look for grit gravel.

Do you usually find it at Canadian Tire or Home Depot?

[Gilbotron]

I call it grit but I think its called coarse gravel. Its actually a smaller grain gravel thats in the standard pea gravel colours. I've only ever been able to find it at Pet Smart and its a National Geographic brand.

[Plants245]

Not sure if I am too late to get in on this:

I am not sure the size of pea gravel, but I use peace river gravel (https://angelfins.ca/index.php?main_page=product_info&products_id=1437) mixed 50/50 with flourite.

[Greg_N]

Natural pool filter sand from piscine works well and is super cheap. I've used it for a few years on many dirted tanks quite successfully