Short answer
What is the difference between shock and a floating dispenser?
Shock is an oxidizer in granule form that goes into circulating water to break down residue from soaking. A floating dispenser is a device that floats in the spa and releases chlorine or bromine tablets over time. One is a periodic addition, and the other is a steady release device.
Shock vs floating dispenser for hot tub is a choice between a burst of oxidation and a slow, steady release of sanitizer. Shock granules go into the water to break down the residue left after soaking, while a floating dispenser drifts around the spa and releases tablets over time. Pick shock when the water needs a reset after heavy use, and pick a dispenser when you want steady sanitizer between soaks.
This comparison covers how each side works, what the listings state, and where each routine fits, with the listings as concrete examples. Listings were collected 4 November 2026.
This article is informational and is not medical advice. Hot tub water care uses chemicals that need careful handling and storage, so follow the directions on each listing. See the Medical Disclaimer.
Chillveda earns a commission when you buy through links on this page, at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. Affiliate disclosure.
Quick picks
-
1
AquaDoc Non Chlorine Hot Tub Shock Chill Score 9.6/10Check price on AmazonA 10 lb oxygen based non chlorine shock that dissolves quickly and supports bromine and chlorine systems.
-
2
PROFELIZ 5.5LBS (2 Pack) Non-Chlorine Spa Shock Chill Score 9.6/10Check price on AmazonA 2 pack of non chlorine shock oxidizer granules, 2.75 lbs in each bottle, for hot tubs, spas and pools.
-
3
Pool Chlorine Floater, 7.5" Large Floating Chill Score 9.6/10Check price on AmazonA large floating chlorine dispenser in durable ABS plastic with an adjustable control ring, holding up to 4 pieces of 3 inch tablets or sticks.
-
4
U.S. Pool Supply Floating Spa Chill Score 9.6/10Check price on AmazonA heavy-duty weighted floating dispenser for 1 inch chlorine or bromine tablets, with 13 flow level control settings.
A 10 lb oxygen based non chlorine shock that dissolves quickly and supports bromine and chlorine systems.
Pros & ConsViewHide
Pros
- 10 lb size for routine spa maintenance
- Dissolves quickly with no pre mixing stated
- Supports both bromine and chlorine systems
- Helps break down oils, lotions and cosmetic residue
Cons
- No warranty term is stated
- Container measures 10.0 inches on each side, so it needs storage room
- An oxidizer for routine care, not a continuous sanitizer feed
- No dispenser included for steady tablet release
A 2 pack of non chlorine shock oxidizer granules, 2.75 lbs in each bottle, for hot tubs, spas and pools.
Pros & ConsViewHide
Pros
- Two bottles, 2.75 lbs each, for repeated care
- Granules dissolve quickly in water
- Listing states clear water in 15 minutes
- Chlorine free formula for hot tubs, spas and pools
Cons
- No warranty term is stated
- Spec table lists Size as 2.75 lbs while the title gives the 5.5 lbs pack total
- Granules must be added to the water, not left to float
- No dispenser included for steady tablet release
A large floating chlorine dispenser in durable ABS plastic with an adjustable control ring, holding up to 4 pieces of 3 inch tablets or sticks.
Pros & ConsViewHide
Pros
- Holds up to 4 pieces of 3 inch tablets or sticks
- Adjustable control ring for balanced delivery
- Durable ABS plastic, listed as lasting for years
- Floats to reach every corner of the pool
Cons
- Tablets not included
- No concrete warranty term is stated
- Flow depends on the adjustable control ring setting
- Pack holds 1 dispenser only
A heavy-duty weighted floating dispenser for 1 inch chlorine or bromine tablets, with 13 flow level control settings.
Pros & ConsViewHide
Pros
- 13 adjustable chemical flow control settings
- Weighted cap helps keep it clear of the filter
- Flat top lays flat under solar covers
- Holds 1 inch chlorine or bromine tablets
Cons
- No warranty term is stated
- No dimensions are stated
- No item weight is stated
- Tablet count per fill is not stated
Shock vs floating dispenser for hot tub at a glance
| Shock | Floating dispenser | |
|---|---|---|
| How it works | Granules added directly to circulating water | Floats in the spa and releases tablets over time |
| What goes in the water | Oxidizer granules | Chlorine or bromine tablets |
| When it helps | After soaking, when residue clouds the water | Between soaks, for steady sanitizer |
| What to watch | Needs adding again for each round of care | Release depends on the control setting |
| Storage and handling | Containers need dry storage room | Dispenser floats in the spa |
How shock works
The AquaDoc example is a 10 lb oxygen based non chlorine shock that dissolves quickly and can be added directly to the hot tub while the water is circulating. The listing states it helps break down oils, lotions and cosmetic residue that can lead to cloudy water, and it supports bromine and chlorine systems without increasing chlorine levels.
The PROFELIZ example is a 2 pack of non chlorine shock oxidizer granules, with 2.75 lbs in each bottle. The listing states the granules dissolve quickly and clear the water in 15 minutes, and it suits hot tubs, spas and pools.
Shock is a periodic addition, not a continuous feed. It oxidizes the organic buildup that soaking leaves behind, while the steady sanitizer role belongs to a dispenser or another system. For the wider sanitizer picture, see the bromine vs chlorine for hot tub comparison and the shock vs chlorine for hot tub comparison.
How a floating dispenser works
The Merkia example is a large floating dispenser in durable ABS plastic with an adjustable control ring. The listing states it holds up to 4 pieces of 3 inch chlorine or bromine tablets or sticks at once, and it floats so it can reach every corner of the pool.
The U.S. Pool Supply example is a heavy-duty weighted floating dispenser for 1 inch chlorine or bromine tablets. The listing gives it 13 flow level control settings, and its flat top allows it to lay flat under solar covers while the weighted screw on bottom cap keeps it clear of the filter.
A dispenser keeps releasing while it floats, so its job is steadiness rather than a single burst. The control setting adjusts how much chemical reaches the water, while a full fill decides how long one fill lasts.
Gear for each route
These are scored on the Chill Score, which weighs performance, build and value most, with safety where it applies, and warranty. No product states a safety certification, so safety adds nothing for any pick here. No product states a warranty term, so warranty adds nothing either.
| Product | Chill Score | Perf. /35 | Build /25 | Value /25 | Safety /10 | Warranty /5 |
|---|---|---|---|---|---|---|
| AquaDoc 10 lb Shock | 9.6 | 30 | 21 | 21 | n/a | 0 |
| PROFELIZ 5.5 lb Shock | 9.6 | 29 | 20 | 21 | n/a | 0 |
| Merkia 7.5 in Floater | 9.6 | 28 | 21 | 20 | n/a | 0 |
| U.S. Pool Dispenser | 9.6 | 28 | 21 | 19 | n/a | 0 |
Scores run from 9.2 to 9.8: each product’s point total is placed on that range, so more points always means a higher score. Safety counts only for powered gear or where the listing states safety features; where it does not apply, the score is taken over the remaining 90 points.
Choose shock if
- You want a reset after soaking, when residue clouds the water.
- You want a chlorine free oxidizer for routine care.
- You prefer granules that dissolve quickly.
- You have dry storage room for a container or a 2 pack of bottles.
Choose a floating dispenser if
- You want steady sanitizer between soaks without adding granules each time.
- You use chlorine or bromine tablets and want an adjustable release.
- You want a full fill that stretches the time between refills.
- You want a dispenser made for a spa or hot tub.
Check Your Space First
- Measure shelf room for the AquaDoc container, which the listing gives as 10.0 inches on each side.
- Leave room for the PROFELIZ bottles, each listed at 3.07 inches by 3.07 inches by 9.13 inches.
- Check that a floating dispenser fits under a cover, since the U.S. Pool Supply dispenser has a flat top that lays flat under solar covers.
- Keep granules and tablets dry in storage, and keep the Merkia dispenser where its 7.5 inch body can float freely.
Common questions
What is the difference between shock and a floating dispenser?
Shock is an oxidizer in granule form that goes into circulating water to break down residue from soaking. A floating dispenser is a device that floats in the spa and releases chlorine or bromine tablets over time. One is a periodic addition, and the other is a steady release device.
Can shock and a floating dispenser serve the same spa?
The listings describe different jobs, so the two sides are not substitutes for each other. The AquaDoc listing states its shock works alongside bromine and chlorine systems. A dispenser, by contrast, holds the tablets that supply sanitizer over time. See the hot tub water care system roundup for the wider routine.
What size tablets do floating dispensers hold?
The Merkia dispenser holds up to 4 pieces of 3 inch tablets or sticks. The U.S. Pool Supply dispenser holds 1 inch tablets. Check the listing for the tablet size before buying, since the two dispensers here take different sizes.
How do you add shock to a hot tub?
The AquaDoc listing states its shock can be added directly to the hot tub while the water is circulating, with no pre mixing. The PROFELIZ listing states its granules go directly into the water and clear the water in 15 minutes. Follow the directions on the listing for the product you buy.
Which side needs more storage room?
The AquaDoc container measures 10.0 inches on each side, so it needs more shelf room than the other picks here. The PROFELIZ pack is two bottles, each listed at 3.07 inches by 3.07 inches by 9.13 inches. The Merkia dispenser measures 7.5 inches by 7.0 inches by 5.0 inches, and it lives in the water rather than on a shelf.
Back to all hot tub accessories reviews.
