Cold plunge accessories don’t compete with each other. A thermometer, a filter, and a cover each solve a different problem, and most owners end up with several.
The catalog prices here run from $15 for test strips to $499 for a locking insulated cover. This guide covers what each accessory does and what to check before you buy. Each section has its own deeper article.
Short answer: buy a thermometer and the right filters first. Add a fitted cover if the tub lives outdoors, and a locking one if children can reach it.
What’s in the category
| Accessory | Example | Price (per listing) | Fits |
|---|---|---|---|
| Thermometer | Ice Barrel thermometer | $17.99 | Any tub |
| Wireless thermometer | TempPro TempAir | See Amazon | Outdoor tubs |
| Test strips | AquaChek 7-Way, 100 strips | See Amazon | Chlorine or bromine tubs |
| Ice molds | Haldane block molds, 2-pack | See Amazon | Ice-only tubs |
| Test strips | Sirona Water Test Strips | $15 | Any tub |
| Sanitizer stick | Renu Sanitizing Spa Stick | $27.99 | Check with Renu |
| Filters | Plunge Filter Pack, 6-pack | $46 | Plunge All-In and Pro Chiller |
| Water treatment | Renu Pure Water Treatment Kit | $75 | Check with Renu |
| Insulated cover | Plunge XL Spa Cover | $218.90 | Listed Plunge tubs |
| Weather cover | Renu Total Protective Cover | $269 | Renu Cold Stoic and Siberian |
| Annual supplies | Renu Annual Maintenance Package | $299 | Cold Stoic Classic, 2.0, standard Siberian |
| Locking cover | Renu All-Weather Insulated Cover | $499 | Check with Renu |
| Step | Ice Barrel Step Stool | Not in our data | Ice Barrel tubs |
Prices from Ice Barrel, Plunge, and Renu Therapy listings, checked September 2026.
Thermometers
Cleveland Clinic says beginners should start at 50 to 59°F, that you should avoid going below 40°F, and that you should use a thermometer to make sure you’re in a safe zone.
That makes a $17.99 thermometer the first purchase for an ice-only tub. With a chiller, it’s a second opinion on the display. For a tub outside, the TempPro TempAir sends the reading to a display indoors; TempPro rates it ±0.9°F from 32 to 140°F.
Filters
A chiller pulls water through a filter all day. Plunge says operating without a filter or with a dirty one can shorten the life of the chiller and may void the warranty.
Check two things:
- Which filter fits. Plunge’s All-In and Pro Chiller filter is 30 micron and NSF-50 rated. Plunge says it isn’t compatible with its Standard or first-generation chiller.
- How long one lasts. Renu Therapy says its standard filters last 2 to 6 weeks in home use, and that most customers change them every 2 to 3 weeks.
Water care
Here’s what the spec sheet won’t tell you: water care depends on the tub more than on the product.
Renu Therapy says its tubs have a built-in ozone generator and filter, and that this removes the need for chemicals. It still sells an optional mineral stick ($27.99, about 3 months) and a treatment kit ($75). A tub with no filtration needs more from you.
For a reference range, CDC recommends pH 7.0 to 7.8 for pools and hot tubs. Renu’s test strips print a target of 7.2 to 7.8. For a tub sanitized with chlorine or bromine, AquaChek’s 7-way strips read both, plus pH and alkalinity, 100 to a bottle.
Covers
A cover keeps debris out. An insulated one also slows the water warming between sessions. A locking one adds child safety.
| Plunge XL Spa Cover | Renu Total Protective Cover | Renu All-Weather Insulated Cover | |
|---|---|---|---|
| Price | $218.90 | $269 | $499 |
| Insulated | Yes | Not stated | Yes, foam |
| Locks | Not stated | Not stated | 4 latches with child locks |
All three are sized for their own brand’s tubs.
Child safety
CDC says more children ages 1 to 4 die from drowning than from any other cause. The CPSC’s barrier guidelines count spas and hot tubs as pools. Treat a filled cold plunge the same way.
Steps
The Ice Barrel Step Stool is 16 inches tall, holds 300 lbs, and has a non-slip surface. It’s made for Ice Barrel tubs, and its price isn’t in our data.
How to shortlist
- Write down your tub’s brand, model, and generation.
- Buy a thermometer.
- Find the filter your chiller takes and how often the maker says to change it.
- Read what the maker says about water care before buying chemicals.
- Outdoor tub: add a cover that lists your model.
- Children at home: make it a locking cover.
If you’re still choosing the tub, start with the cold plunge buying guide. For tubs without a chiller, see the ice bath buying guide.
Bottom line: fit comes first. An accessory that doesn’t list your tub model isn’t a bargain at any price.
Sources
- Cleveland Clinic, “Are ‘Cold Plunge’ Ice Baths Good for You?” May 8, 2026: health.clevelandclinic.org
- Plunge, Filter Pack (All-in and Pro Chiller) product page, accessed October 8, 2026: plunge.com
- Renu Therapy FAQ (filters, ozone system, water changes), accessed October 8, 2026: renutherapy.com
- CDC, “Home Pool and Hot Tub Water Treatment and Testing,” May 10, 2024: cdc.gov
- CDC, “Preventing Drowning,” September 29, 2025: cdc.gov
- U.S. Consumer Product Safety Commission, “Safety Barrier Guidelines for Residential Pools” (Pub. 362), accessed October 8, 2026: cpsc.gov
- Specs and prices: Ice Barrel, Plunge, and Renu Therapy listings, checked September 2026