Fritz Mardel Maracyn Oxy Fish Aquarium Treatment, 4-oz bottle

Deal
Skip image gallery
Slide 1 of 2

$6.75 First Time Autoship Price
this order
Save 35% (up to $20) today when you set up Autoship. 
$10.39 Autoship Price
future orders
  • Get deliveries on your schedule
  • Skip, change, or cancel anytime
$10.39 Chewy Price
($2.60 /oz)
Save $2.60 (-20%)
$12.99 List Price
Promo, New Customers Only: Spend $49+, Get $20 eGift Card + Free Shipping with code: WELCOME
In Stock
FREE 1-3 day delivery on first-time orders over $35
Free 365-day returns

No interest if paid in full in 6 months on PayPal purchases of $149+. .

About This Item

Details

  • This treatment effectively combats true fungal infections and bacterial diseases.
  • This is a non-antibiotic formula that is safe for most invertebrates and plants.
  • You and your fish will appreciate that this treatment is fast-acting and easy to use.
  • For versatility, it’s suitable for both freshwater and saltwater aquariums.
  • This formula treats a variety of issues, including saprolegnia, ichthyosporidium, egg fungus, and fin and tail rot.

Frequently bought together

Questions & Answers

4 Customer Questions

Can it be used on cats?

Answer by Chewy • Mar 19, 2025
This product is specifically made for fish.

Will this kill the beneficial bacteria? Also, is it safe for scaleless fish?

Answer by Chewy • Aug 25, 2025
Maracyn Oxy does not inhibit the biofilter, but it is always good practice to monitor water parameters when using any treatment. It is safe for scaleless species.

What are the ingredients?

Answer by Chewy • Aug 15, 2025
Maracyn Oxy is a solution of sodium chlorite with a proprietary formulation.

Is it safe tor frogs?

Answer by Chewy • Aug 04, 2025
It is not recommended to use MaracynOxy for frogs, as they have not conducted the studies to determine if safe.
Reviews
Write a Review
4.5
Rated 4.5 out of 5 stars
14 Ratings
Terms & Conditions

5 Customer Reviews

Rated 3 out of 5 stars
By Gail on Dec 6, 2025

Not Recommended for Planted Tanks

It worked to clear fungus from fish but also killed a beautiful tiger lotus plant and negatively impacted all the plants in the tank. I also have not seen several

It worked to clear fungus from fish but also killed a beautiful tiger lotus plant and negatively impacted all the plants in the tank. I also have not seen several large snails and suspect they died too.

Rated 5 out of 5 stars
By Dina on Jul 18, 2025

This stuff worked and I didn't think anything would!

I saw this hemorrhage on my pleco about 6 months ago. It started as a small spot on her stomach. I let it get to this point not knowing what was going on. After

I saw this hemorrhage on my pleco about 6 months ago. It started as a small spot on her stomach. I let it get to this point not knowing what was going on. After researching, I was pretty sure that I was going to lose my pleco AND now one of my tetras had a whole bunch of her insides hanging out of her gills....horrible! Both are well on their way to recovering. I didn't think that the fish with the inside-out, bloody gills was going to survive, but he's eating and happily swimming like normal. I followed the directions (it says 5 days, I did 9). It warned against it, but I had really sick fish and had to do something. It was a complete shot in the dark but, I'm happy I chose this product, I'm pretty sure it saved my entire fish tank.

Rated 4 out of 5 stars
By Valerie on Sep 4, 2025

Good

Attempted to use it to combat algae and didn’t rlly work for that purpose.

Attempted to use it to combat algae and didn’t rlly work for that purpose.

Rated 5 out of 5 stars
By Donna on Jan 12, 2026

Very good

Worked in just a few days

Worked in just a few days

Rated 5 out of 5 stars
By Marion on Aug 7, 2025

Good stuff

Great for your tank.

Great for your tank.