"the soil seems too dense and holds water too long."

Folks are quick to say "over-watered".

Without examining variables, that's not very helpful.
Mo' betta to explain why dey stay wet.

No worry about the sand.
We do not want to lose water to evaporation, we want the plant to use every drop for transpiration.

When there is way more soil than root, the plant can not suck the soil dry.
Water that stays for days loses dissolved air and goes stagnant.

Fungus gnats are "scent hunters".
They sniff for signs of weakness, and that's where they lay their eggs.
The larva damage feeder roots.
Root damage changes the soil:root ratio.
Water stagnates, roots die, gnats smell dat.
Downward spiral.

Dryer sheet on top of the sand bollixes their "nose".
I've seen them do U-turns as soon as the approach a sheet.
Same thing with other scent hunters like mosquitoes!
(I rub my dogs with dryer sheet during mosquito season)

But, I digress.Attachment 292506

The soil:root ratio is the reason that we start in small containers and then re-pot several times.
A healthy plant, with healthy roots is hard to overwater.
Hard to drown when dey almos' rootbound.

So, my advice is do not transplant too early or in too big a step.
And, of course, give less water to damaged plants.
Most new growers see a distressed plant and try to fix it by "giving" water, nutes, mendicants and light.
All of which exacerbate the original problem
The soil needs to be a little dry so the new "Water roots" have to grow to find some.
And so that the remaining roots can breathe.

If the soils is evenly wet and saturated with nutes, all the time, there's little incentive to produce more roots.
As a rule, healthy plants, with a good soil:root ratio, will need fresh water every couple days or so.

Figured this out when I grew in DWC.
Was able to actually see the root development over time.
I teased the roots with faint nutes until they filled the bucket.
Attachment 292507
Then I put on a spread.

Careful observation is the root of knowledge.

@Shove: That's no way to talk about a lady.

@Shaggy. Please read the entire thread before "helping".

Don't mean to sound pedantic, but I am, so that's how it comes out.

Aloha,
Weeze