Should I re-do my substrate?

[Mustangfreak]

Right now I have a 14g cube (15" square) and the substrate is white sand. I have a few different plants, temple, ludwigia repens, ludwigia super mini reds, rotala indica, hornwort, and pennywort. I have this light https://www.amazon.com/gp/product/B08SBPVXCW/?tag=ff0d01-20 and for nutrients, I put Flourish tabs under the sand a week ago.

So far my only issue is my ludwigia repens are losing their leaves from the bottom to close to the top. Only the top has leaves still. I read online that ludwigia repens cant do well in sand since it compacts too much for its roots. Should I remove my sand, place down gravel, and then a small layer of sand? (I prefer its looks over gravel).

My wife has the same tank and plants, but has gravel instead and her plants are doing amazing!

Or should I use a different substrate all together like a plant specific substrate?

 

[Byron]

The problem with the Ludwigia is not the substrate, it is more likely the light. Stem plants are fast growing, and the stem(s) will grow toward the light. If the light is too weak, the lower leaves will die off because the plant is putting its energy into the growing tips where the light is brighter, and light drives photosynthesis. Some regularly pull up stem plants, trim off the lower bare stems, and replant the tips. Alternatively, brighter light may allow the stems to retain their leaves.

Nutrients may play into this too, as fast-growing plants need more nutrients in balance with more light. Substrate tabs will have very little if any benefit for stem plants. Leaves and roots grow from the nodes along the stem. Some nutrients are taken up via the leaves alone or primarily, and liquid fertilizer is beneficial. However, too much of this and problem algae can occur.

To the substrate itself. Sand is about the best substrate for most fish, and all plants. Gravel can provide a habitat-correct substrate for certain fish (livebearers for example), but plants will grow in most any substrate provided the grains are not too large. Pea gravel is the largest grain size you want, and some plants will not do a s well in this. But sand is fine for all plants. However, white sand is not a good choice. Plants won't care, but fish do. No natural habitat where our fish come from has white sand for the substrate. Many fish will be uneasy over a white substrate. Light reflects off the white sand, stressing fish. I find it difficult to view an aquarium with white sand because of this brightness, and the poor fish must have it far worse. A dark substrate is better, and fish colours will be more intense.

So-called plant substrates are frankly a waste of money. They can also create on-going bacterial problems especially for substrate-level fish. Plants will grow well in an inert sand; substrate tabs will help larger plants like swords.

Aquarium river sand, or a quality play sand, are ideal substrate sands provided they are not white.

 

[Mustangfreak]

The problem with the Ludwigia is not the substrate, it is more likely the light. Stem plants are fast growing, and the stem(s) will grow toward the light. If the light is too weak, the lower leaves will die off because the plant is putting its energy into the growing tips where the light is brighter, and light drives photosynthesis. Some regularly pull up stem plants, trim off the lower bare stems, and replant the tips. Alternatively, brighter light may allow the stems to retain their leaves.

Nutrients may play into this too, as fast-growing plants need more nutrients in balance with more light. Substrate tabs will have very little if any benefit for stem plants. Leaves and roots grow from the nodes along the stem. Some nutrients are taken up via the leaves alone or primarily, and liquid fertilizer is beneficial. However, too much of this and problem algae can occur.

To the substrate itself. Sand is about the best substrate for most fish, and all plants. Gravel can provide a habitat-correct substrate for certain fish (livebearers for example), but plants will grow in most any substrate provided the grains are not too large. Pea gravel is the largest grain size you want, and some plants will not do a s well in this. But sand is fine for all plants. However, white sand is not a good choice. Plants won't care, but fish do. No natural habitat where our fish come from has white sand for the substrate. Many fish will be uneasy over a white substrate. Light reflects off the white sand, stressing fish. I find it difficult to view an aquarium with white sand because of this brightness, and the poor fish must have it far worse. A dark substrate is better, and fish colours will be more intense.

So-called plant substrates are frankly a waste of money. They can also create on-going bacterial problems especially for substrate-level fish. Plants will grow well in an inert sand; substrate tabs will help larger plants like swords.

Aquarium river sand, or a quality play sand, are ideal substrate sands provided they are not white.

So should I get a second light so the entire cube has light and not just in the middle?
And I guess I’ll put black sand on my to-do list

 

[AdoraBelle Dearheart]

So should I get a second light so the entire cube has light and not just in the middle?
And I guess I’ll put black sand on my to-do list

Doesn't have to be black sand, even a natural sand colour is usually okay, especially if there's hardscape, almond leaves, and plants providing cover and shaded areas.

It's the trend for brilliant white sands that tends to cause trouble for fish, and the purely black, dyed sands can cause similar problems... I assume because to the fish, that can be hard to perceive as the substrate at all, and could look like much deeper water, where predators might lurk.

Look for something in the middle range, not at either extreme. Anything in the browns/greys natural tones is likely to acceptable to most fish. My sand is technically labelled "black limpopo sand" but in reality is a slate grey, and flecked.

 

[Byron]

Agree with above on the sand. And make sure it is inert, not calcareous. Buff/tan sand, or a dark grey, is fine. I use Quikrete Play Sand which has a dark grey and a tan, available from Home Depot or Lowe's in NA. Not all "play sand" is safe, but this brand Quikrete is.

As for the light...adding another might be too much for the fish, and it can mean algae issues. My process is to take the light I have, use a quality tube (I have fluorescent T8 lighting, LED is another game altogether), and floating plants, then stay with plants that will manage under these conditions. My fish come first.

 

[xxBarneyxx]

I have the larger version of the Nicrew light and its pretty rubbish so that may be part of the issue. Directly under the middle its not terrible (at 12" but at 15" it might not be as great) but the drop off is pretty bad. I measured 7000 Lumens directly in the middle at 12" (in air). Moved forward 3 inches and it dropped to just over 1000 lumens. The drop of to the left and right edge was even worse.

My light meter is not exactly high spec so I wouldn't trust the lumen number it is giving me is correct, however it is enough to see how much the light drops off from these lights.

Personally I would grab another light. You can run them at lower power and turn them up until you get good growth/no algae, or run them at max and turn it down until your plants start to suffer. I would also use some water column ferts, in my experience root tabs can help with some root heavy plants but a mix of water column and root ferts works best. Even very root heavy aquatic plants will still take some nutrients from the water column.

I agree on fish not liking bright light but honestly its not a big deal. Once you have good plant growth going on, chuck in a few floating plants and there will be plenty of cover.

Substrate wise I preferred compost (covered with a substrate like gravel/sand) or aquasoil. In combination with water column dosing you know you've got everything covered and wont have to mess with root tabs for quite some time. It is not necessary though and sand will work fine, especially with water column dosing.

 

[Mustangfreak]

Could anyone suggest a light? I dont know what to look for exactly

 

[seangee]

So far my only issue is my ludwigia repens are losing their leaves from the bottom to close to the top. Only the top has leaves still. I read online that ludwigia repens cant do well in sand since it compacts too much for its roots. Should I remove my sand, place down gravel, and then a small layer of sand? (I prefer its looks over gravel).

A lot of plants do this. When you trim them (probably every 6-12 weeks) lift them out and trim off the bottom. Then replant the stem.