Worried That a Galvanized Tank Might Kill Your Fish? | ZipGrow Inc. (2024)

  • Aquaponics

Worried That a Galvanized Tank Might Kill Your Fish? | ZipGrow Inc. (1)

There are lots of reasons people use galvanized tanks in aquaponics systems. They are cheaper than stainless, they are durable, and they are readily available.Sounds great, right?

Galvanized steel can cause problems in aquaponic systems, however; if you are thinking about using one for your aquaponicsystem, it could save you some trouble down the road to know what you are getting into.

Galvanizing is a process where the manufacturer dips the metal tank in a bath of molten zinc at a temperature of around 840 °F (449 °C). This is usually to prevent corrosion over time, and to provide a cheaper alternative to stainless steel.

What’s wrong with a little Zinc?

Zinc is a common micronutrient for plants. This leads some people to think it is safe for aquaponics systems. While it is true that plants can tolerate pretty high zinc levels in solution, fish cannot.

Worried That a Galvanized Tank Might Kill Your Fish? | ZipGrow Inc. (2)

Water quality guidelines can be found online if you know where to look. We often recommend technical information from ATTRA or the Purdue Agricultural Extension. Purduerecommendslevels of zinc be kept between .03 and .05 ppm. Most fish will become stressed at .1 to 1 ppm, andwill start dying off at 4-8 ppm.

According to theAmerican Galvanizers Association:“The biggest factorsin the zinc corrosion rate in fresh water are dissolved gasses, hardness/mineral rate, flow rate, and other ions/chlorides,hardness of the water and the pH levels.” These factors make it hard to predict exactly how much zinc will be released from your tank.

The aquaponic community has a number of discussions related to this topic. A big thanks toJimmy Ward, of the Backyard Aquaponic community, who shareda detailed description of his strugglewith galvanized steel tanks.

You may have seen examples of someone painting their galvanized tank with a heavy weight epoxy, or a fish safe polymer of some sort (eg.Pond Armor). This has proven successful in some situations, and can be considered if it is too late to choose a different tank.

The danger in this option is that new tanks may have an oily layer left over from the manufacturing process, which makes it difficult for the paint to adhere to the surface of the galvanized. Over time, your system may flake or otherwise allow more zinc into the water. If you have an old tank laying around, you may be able to avoid this problem, although using old tanks can lead to other types of problems.

We have seen enough mishaps in the aquaponic system startup phase to recommend avoiding this solution. Instead, we recommend finding an alternative to galvanized steel tanks.

1. Use a Tank Liner

If you already have a galvanized tank, and you won’t be investing in a new tank, you might choose to line the tank with something.Heavy duty pond linercan be used, although it is a little pricy. Also, to get a good fit you will need tocut and join the seamsusing a sealant (WARNING! Intense elevator music in this tutorial).

2. Build Your Own

If you are handy, you can build your own tank out of plywood using sealants and/or a pond liner. You can get creative with materials and with designs. John Kohler, of Growing Your Greens, gives us a walkthrough on a sweetDIY fish tankon his Youtube channel. This tank was built using just 2×4 lumber and a special seamless coating. Tune in at minute 15:30 to get right to the DIY goodness.

There may be a size limit to how big you can build using your own materials. You may choose a long, trough like design to help keep things manageable. The difficulty is to build a large enough tank while eliminating leaks and weak points.

3. Roto Mold Fabrication

Most regions will have at least one or two roto molding (rotational molding) companies nearby. Common products will include septic or holding tanks. Many companies offer specific products for agriculture, although as long as the materials are neutral they will be fine for fish cultivation. Here is a2,150 gallon tankfor around $1,400. Shipping on this unit was calculated around $400, although many tanks require a custom shipping quote.

4. IBC Tanks

IBC tanks can be a solution for smaller or medium systems. We talk with dozens of growers who have found second hand IBC tanks for under $100. In Denver, you can find hundreds of used tanks available on Craigslist (check out these exampleshere).Many sellers will be selling both food grade and non food grade IBC tanks. Make sure you ask what was in them. Some sellers pre-rinse their tanks, which can save you some labor.

If you can’t find a used one, you canbuy new from uLine. Prices run around $499 for the 275 gallon tank, or $529 for the 330 gallon tank.

Using galvanized steel tanks can be amajor reason that beginning aquaponic growers lose so many fish when they’re starting their systems. This can lead to confusion over the cause of the die-off, as many a seasoned aquaponicgrower knows. If it is not too late, we recommend avoiding galvanized steel tanks altogether.

We hope that this article helps you to avoid mistakes in your aquaponics system.

Welcome To ZipGrow Blog

Our goal is to produce high-quality informative content to highlight the power of local food, small business, and how delicious sustainable food can have in our communities and in our world.

Recent Posts

Bringing Hydroponics to the Classroom: Ayer-Shirley Regional School District’s Innovative Approach to STEM Education

Read More »

Whole Kids Garden Grant Program 2024

Read More »

3 Hydroponic Systems for Classrooms

Read More »

Check Us Out On YouTube!

Worried That a Galvanized Tank Might Kill Your Fish? | ZipGrow Inc. (6)

Enjoyed This Post? Sign up for our Newsletter

Subscribe today to stay updated! Only the good stuff, we promise.

Worried That a Galvanized Tank Might Kill Your Fish? | ZipGrow Inc. (2024)
Top Articles
Latest Posts
Article information

Author: Sen. Ignacio Ratke

Last Updated:

Views: 6236

Rating: 4.6 / 5 (76 voted)

Reviews: 91% of readers found this page helpful

Author information

Name: Sen. Ignacio Ratke

Birthday: 1999-05-27

Address: Apt. 171 8116 Bailey Via, Roberthaven, GA 58289

Phone: +2585395768220

Job: Lead Liaison

Hobby: Lockpicking, LARPing, Lego building, Lapidary, Macrame, Book restoration, Bodybuilding

Introduction: My name is Sen. Ignacio Ratke, I am a adventurous, zealous, outstanding, agreeable, precious, excited, gifted person who loves writing and wants to share my knowledge and understanding with you.