How to Get Rid of Algae Dust in a Pool (in 30 Minutes)

  • By: John Parker
  • Last Updated: November 11, 2022

Any form of algae in a pool is not good news. Algae dust is no exception as once you have dealt with a green pool and killed an algae bloom using chemicals it sits on the bottom of the pool making it look very unpleasant.

To remove dead algae in the form of algae dust from your pool needs a different approach from carrying out a normal clean using a manual vacuum, an automatic cleaner or a robotic pool cleaner.

Getting rid of algae dust is not difficult to do but it does need a little patience. I will explain why you have to use a particular method and how to go about it below.

How to Get Rid of Algae Dust in Pool
Algae dust at the bottom of my pool

Table of Contents

What is algae dust?

Algae dust is actually dead algae that the chlorine sanitizer you used to shock has killed in the pool. Although live algae are normally green (or yellow) when they die they turn a dark brown color.

Algae dust is very fine and settles at the bottom of a pool causing the pool to look very uninviting.

What does algae dust look like?

Algae dust looks like dark brown sludge that accumulates on the bottom of a swimming pool. When you look at it in detail it is comprised of thousands of tiny dead algae particles.

You can tell whether it is algae dust or just dirt by trying to pick a little up between your fingers. If you pick it up easily then it is probably dirt (which is relatively dense). If you find it hard to pick any up as it moves as soon as you try then it is undoubtedly algae dust (which is very fine and light).

how to get algae off bottom of pool

How to remove dead algae from pool bottom?

There are two problems when it comes to removing dead algae in the form of algae dust from a pool:

  1. Since algae dust is very fine and light, it is very easily disturbed when cleaning, causing it to go into suspension in the pool water and then resettle some time later. This then requires further cleaning.
  2. As algae dust is so fine, if it is sucked into the pool’s filter there is a good chance that it will pass through the filter (either a sand filter or cartridge filter) and will then be pumped back into the pool to settle back on the floor of the pool.

The best way to get rid of the algae dust in one go is to vacuum using your pool vac but with the pool filter lever set to the “waste” position rather than on the “filter” system (known as vacuuming to waste”.

This means that the water you vacuum up will be expelled from the pool, rather than passing through the filter and going back in the pool.

Quick guide to vacuuming to waste:

  1. Top up the pool water. When you vacuum to waste, since the water is expelled from the pool’s system, the water level will drop quite quickly so you should raise the water level well above normal using a garden hose before vacuuming to allow for this. It is a good idea to leave your garden hose running into the pool while vacuuming too.
  2. If there is any algae dust on the rungs of your pool ladder, steps or any other flat pool surfaces above the bottom of the pool then gently use a pool brush to sweep these to the floor of the pool.
  3. Set up the vacuum using the vacuum head, vacuum pole and vacuum hose then insert the free end of the vacuum hose either into a pool skimmer or into a dedicated pool port if you have one.
  4. Set the multiport valve of the filter to the waste position and switch on the pool pump
  5. Start to vacuum but try to move the vacuum head along the bottom slowly in order to disturb the algae dust as little as possible. Any algae dust that is disturbed will probably float in the pool water and then settle again later which you will want to avoid since you will probably then need to vacuum again.
  6. When you have vacuumed all of the algae dust up, switch off the pump, disconnect the vacuum and, if necessary, continue topping up the pool water level until it is at a normal level (roughly halfway up the skimmer opening).
  7. Now test your water chemistry and add any chemicals that may be necessary to bring the levels back to normal.
how to remove dead algae from pool bottom - vacuum to waste

For full details of how to do this, I suggest you read my post Vacuuming to waste – step by step guide or watch my Youtube video How to vacuum to waste.

Will a robotic pool cleaner remove algae dust?

I have a Dolphin pool cleaner which does a great job of cleaning my pool under normal circumstances. Athough it will trap any algae dust it picks up as it cleans (with a set of fine filters in the cleaner) I do not actually use it when I have algae dust to remove.

The reason is that when a robotic pool cleaner moves around it actually moves quite a lot of water. This water movement disturbs the fine particles of algae dust that then float in the water for some time before coming to rest on the bottom of the pool again.

You then have to run the robotic pool cleaner through another cleaning cycle (or perhaps more than one) to finally get rid of all of the algae dust.

It is much quicker, in the long run, to manually vacuum to waste.

Can you use an automatic pool cleaner to remove alage dust?

Although automatic pool cleaners generally do not disturb the water too much as they clean they would probably do a good job of removing the algae dust.

However, as you would still need to use the waste setting on the filter, the pool’s water level is likely to drop substantially before the pool cleaner had covered the entire bottom of the pool. So manually vacuuming to waste would be the best method.

Should you swim in a pool with algae dust?

Because the algae are dead, algae dust may not present a health problem to swimmers as such. However, because algae dust particles are very fine, swimmers will inevitably disturb them from the bottom as they swim or walk so the pool will soon become brown and cloudy.

You should therefore clean the pool using the method above before swimmers are allowed in the pool.

Pool Maintenance Course

When I first bought my house with a swimming pool, I knew nothing about cleaning and maintaining it. I was recommended Swim University’s Pool Care Handbook and video course so I bought it and have never regretted it.

It was probably the best money I spent that year as I have saved thousands by doing it myself.

Further reading

Too much algaecide in pool

Can you swim 12 hours after shocking pool

Algae dust FAQs

What causes algae dust in pool?

Algae dust is dead algae that settle on the bottom of a pool after treating a green pool with shock to kill algae.

Will a sand filter catch algae dust?

Dead algae particles are very fine so it is extremely unlikely that a sand filter will be able to trap it. If a pool with algae dust at the bottom is vacuumed on the filter setting then much of it will pass through and end up back in the pool. To remove algae dust, vacuuming to waste is the best method.

How do you clean dead algae from bottom of pool without vacuum?

Removing dead algae dust from the bottom of a pool if you cannot vacuum will be extremely difficult. You could try to scoop it up with a very fine pool net but you will probably disturb more than you pick up which will then eventually just settle back on the bottom of the pool.