# Eco-Complete and gravel? Question

#### Jrobber

##### Well Known Member
For a planted tank, would it be fine to put a layer of Eco-Complete on the bottom and cover it with fine gravel?

I need 70 lbs of substrate and trying to setup a tank without breaking the bank too much.

#### ryanr

##### Moderator
Depending on what fish you want to keep, I see no reason why you couldn't do this.

The gravel size will be determined by fish, in that some fish like to dig around, so you don't want gravel that the fish couldn't pass.

But many people use a layer of substrate with gravel on top for their planted tanks.

#### Jrobber

##### Well Known Member
Awesome, I'm still not sure what type of fish I want to keep, but I am leaning towards livebearers.

Thanks ryanr. I just wanted to make sure I could use gravel too, because we're talking about a \$10 difference per bag.

Do you think one 20 lb bag of Eco-Complete would satisfy a tank 36" long and need to be 2-3 inches deep? The reason I ask is I believe there will be nearly 2+ inches of gravel on top of the Eco-Complete. Will the plants roots grow down that far?

#### ryanr

##### Moderator

Multiply aquarium length by width to give cm2 (square centimeters)
Then multiply that by desired depth (in cm) to give cm3 (cubic centimeters)

So (in my tank for example), Length = 60cm, width = 30cm = 60 x 30 = 1800cm2

Desired substrate depth 5cm (~2in) = 1800 x 5 = 9000 cm3

I think Eco-complete has roughly the same volume as Seachem's Flourite, whereby 1kg = 1000cm3, thus I needed 9kg of Flourite (9000cm3 / 1000cm3)

I think Eco-complete quote 1 pound per gallon for a 3inch substrate, but that's subjective, i.e. a 20H will require less than a 20L

HTH

As for the plants growing down that far, I'm not 100%, but I would think they would, provided they are planted deep enough. The best people on here to answer that are probably Nutter and Nate

#### Jrobber

##### Well Known Member
Hmmm.....I think we have a communication breakdown. Lol. You use metric while and I haven't used metric for probably 10 years. Let me try this:

If I use 2.5 cm of Eco Complete to cover the bottom of the tank, then put 5.0 cm of gravel on top of that, will the Eco Complete still work?

#### ryanr

##### Moderator
You guys and your dodgy USA ways of measuring.... lol hahah .

If it were me, I'd go with 2 inches of substrate, 1 inch of gravel (yes more expensive).

Depending on the size of the gravel, many plants will grow quite succesfully in a 3mm (1/8") grain sized gravel, they just do better in a substrate.

Think of it this way, if you have a potted plant in your garden, and use a small layer of potting mix, and fill with gravel, it's probably not going to do as well....

#### Jrobber

##### Well Known Member
Gotcha. More Eco-Complete then cover with gravel.

Does Eco-Complete breakdown over time and lose its nutrients?

#### ryanr

##### Moderator
Nutter uses eco-complete and would have first hand experience, but my thoughts are that the nutrients will be used up by the plants over time, and then you would need to fertilise (with root tablets)

#### Jrobber

##### Well Known Member
Alright, thanks for you help Ryanr.

#### ryanr

##### Moderator
you're welcome

Be sure to post some pics!

#### Nutter

##### Fishlore VIP
Eco-Complete will be fine used underneath gravel, depending on the fish you want. I do it that way myself these days. Choose a fine gravel as Ryan mentioned. I don't know what the dimensions of the tank are so I can't really say how much Eco you should use but you need to have a minimum of 1" of it under the gravel for it to have any real benefit. 2" Eco under 1" gravel will give you much better resullts.

Eco-Complete does not break down, but the nutrients will get used up over the first few months. Eco will supply iron long term but the other nutrients need to be 'topped up' by using substrate fertilizer tablets or liquid fertilisers periodically. Think of Eco-Complete like you would a potted rose. You buy top quality potting mix with all the nutrients in it for the rose to thrive. After awhile though, the rose has used all of those nutrients & you need to add some fertilizer to top up the nutrients in the potting mix again for the rose to continue to thrive.

Ryan, Flourite is exactly the same, long term source of iron but the other minerals are used up within the first 3-6months. Treat it the same way as Eco-Complete.
LOL "dodgy USA ways of measuring". Couldn't agree more. I get a headache trying to do the coversions half the time. Metric is so much easier.

#### Jrobber

##### Well Known Member
Cool. I figured it up last night and I'm going to go with 2" (or 5.1 cm) of Eco and 1" (2.5 cm) of gravel laid on top. Thanks for you help guys.