Backyard Aquaponics
A place to discuss aquaponics

Hello all! I am a third-year Agriculture teacher in Virginia and have been working to bring the system I inherited back to life. I have never had hands-on experience with a system, so this is a learn as I go.

We have a Crop King brand system with a 200+ gallon tank and 4x8 grow bed using Hydronton as a continuous flow system.

After resealing the pips and fixing any leaks, we currently have 10 small goldfish living in the system for a week.

Today we started washing and putting the Hydroton back into the grow bed. Even after washing it, the water has become filthy. Currently, most of it is floating, but I hope as we add the rest, it will push down what is below it and fill the bed.

After 24 hours and reducing the water level a bit, the Hydroton is not floating as bad. The water is starting to clear up a bit but I would love any suggestions for helping this along.

I would love any input and advice. We don't want to use goldfish; we want something we can eat at the end of the school year, but goldfish was a cheap option, and getting other species seemed to be a challenge this time of year.

I hope you all can help!


A teacher in need!

Hi there!
That is cool to inherit a system, without having to raise funds for it, well I guess that can be fun too, and a good learning experience for the kids!

Anyhow, I'd consider your growbed. It seems like the hydroton is a few inches lower than the capacity.
I'd add something to increase this personally, just to try to max out the surface area for the bio beasties to do their thing.
Hydroton is nice, but there are other options of course. River rock or gravel could work, but you'd want to test it to make sure it isn't limestone based rock. People test with vinegar to see if the rock fizzes, if you do a search here you can find posts on it.
Lava rock, or scoria could be used.
Or, maybe you have expanded shale available.
I'd look at your local rock yard and see what they have.

It's hard to tell in the pic, but how deep is the GB?
The more gravel/ rock/ hydroton you have, the more fish you can stock in theory. But if you are jus starting out, and considering that its in a school, you might want to go with less fish = less room for disaster to strike.

As for fish, search your area's fish farms and see what's available.

I would think that you could get catfish, brim/bream/sunfish/bluegill, or maybe bass. I imagine you get very hot temps towards the end of the school year.
So you would probably do well with something that can handle both. Advanced fingerlings would be the way to go.

Every fish has it's ups and downs.

What are your temps like?
Greenhouse/ water?

Is the greenhouse passive? Or heated?

My experience with tilapia is limited but they might be a good option if the temps aren't too low.
They are usually tolerant of beginners mistakes, and if they are given an optimum environment consistently, they can grow quite fast.

How many months of school are left for you? 5-6?
Would you have access over summer?
Power over summer?
Will you be able to keep it running over summer?
If you can, maybe you could cycle the system now. Then feed with compost tea, worm tea, and/ or other nutrients this year, essentially running it like hydropoincs, keep it running over summer, then start with fish at the beginning of next school year, and have a good ten months of growout time, with a robust biofilter in motion.


If your school year is anything close to here, you might have 5 or 6 months left.
Your chances of growing big fish in that time are slim. Most fish seem to take 8 months to a year to reach a good eating size from what I've seen. NOT that it's IMPOSSIBLE! Every situation is different, and with a fast growing fish like Tilapia, and enough heat, maybe you could.

I once was told that Bass can grow just as fast as tilapia in the right conditions. This was from somebody who had experience with both, and he said that the bass actually surpassed the tilapia.

What is your experience level with keeping fish?

Thanks for taking the time to reply!

As far as the GB, it is about a foot deep. The material that goes on top of the hydroton lava rock is an option for me, but the cheapest option would be perlite. I do not think floating would be an issue since the water level would be much lower than this material. If the material does not need to wick water, I am sure river rock is a local option.

I spoke to my local extension agent at VSU and was told I could order bluegill fingerlings but not until the spring from local producers. My tank is currently in the mid-'60s, with the greenhouse being heated to 70 degrees currently. In the summer, it can get scorching with just passive fan cooling. I am not sure how warm the water would get, but the greenhouse gets into the 120s for sure.

I am a 12-month employee and hope to have a student who wants to take on the system as part of their FFA SAE or I will be there to take care of it during the summer.

The goal for the GB is leafy greens produced year-round.

Thanks for the help!

No problem!

Perlite might be okay. I am using pumice in one bed, which I originally thought was perlite, it looks similar, and I had it sitting for so long before I used it, so I forgot what it was. It was inexpensive, and has good surface area, as it's somewhat porous. It is uniformly about 5/8 inch size. It is more sturdy than Perlite in my opinion, and less likely to float, though some of it does for a while. I experienced this while washing it. But, it didn't float in the bed.

River rock would be fine if it passes the fizz test. Maybe 1/2 inch, or perhaps pea gravel if it's not too small? I'd try not to go with large river rock. I think 1/2 inch to 3/4 would be good. You want surface area.

I think some people here have had issues with pure pea gravel clogging with fish waste. But it should be okay on top.

If your department has money to spend, hydroton would work too!

I've had good luck finding used and new hydroton for great prices, or even free on Craigslist and Offerup. You never know what you might find.

The top few inches don't need to be wet, unless you are germinating seeds in the beds. It might be a good idea to mix in what ever you choose, so you have the hydroton reaching the surface. In my experience, it seems to wick a bit, if you choose to throw some seeds in, they usually germinate well.
I eventually added some hydroton to the top, just cause my water level was a bit high, and I didn't feel like cutting the stand pipe.

As for the fish, Bluegill , I think take about a year or a little more to reach a good eating size.

The temps are nice right now in your greenhouse. Consider getting a shade cloth for the hotter months. You could hang it inside, or drape it over.

You would probably be able to add more ventilation with some thought.
I have worked in a greenhouse with similar summer temps, which just had solar fans and small vents on either end. It would actually kill plants.
We added wax piston greenhouse
vent openers, which are activated by melting wax in the piston cylinder. They close as the wax hardens as it cools down. We had to modify the greenhouse a bit to add them.

They work really well, and greatly helped lower the temps on hot days, along with shade cloth.

Leafy greens should do well. Right now the temps sound perfect for most.

You can try more heat tolerant types for the warmer months. Collards/ Chard/ Amaranth greens/ Kale/ Basil would probably be okay. There are some heat resistant lettuces out there, but they might be harder to find.

Does the system just pump to the growbed? Or is there any other kind of filter in between?

Looking at the system again,

can you explain the plumbing? I'm just curious about the layout.

I can't tell much besides the water dumping into the fish tank.

It is a continuous flow system. Goes out of a drain at the bottom and spills into the grow bed. Moves across and out of the lower pipe at the end and then is airlifted into the fish tank again. The system seems to be regulating its self at the moment. The lettuce and winter greens in the bed are growing extremely fast for the light levels right now.

I think once this crop is finished I will add more material. I like the idea of a wicking substance on top of the hydroton and will probably use perlite because of the cost but I will look for used materials!

If you decide to go with perlite, you might want to get the finer aggregate out. It might not be a problem for a while, but it might eventually work its way through the bed and into the water, or end up creating less pore space between the hydration....I don't know for sure, just speculation, and ideas. You don't know until you try!!

I was thinking this might possibly end up clogging a pump eventually, though it does tend to float. And, it sounds like there isn't really a pump involved in your system. I might just be blabbering on.....yeah, probably.

A lot of people adjust the height of their stand pipe to start seeds in the bed, and a lot of people keep the first few inches of depth dry to prevent algae growth, which can cause problems later with ph and oxygen level fluctuations as far as I understand.

I wonder if wicking at the surface would increase evaporation??

As a side note, I have seeded directly into hydroton without any issues.