Abstract: Filtration is the most commonly over-sized or under-sized component in a B2B aquarium project. Buyers size by tank volume. They should size by biomass. I've serviced 300+ filtration failures in 8 years. The root cause is almost always the same: the filter was matched to the glass, not to the fish. And there's a second mistake nobody talks about — buying more filtration than your team can actually maintain.
A hotel restaurant called last week.
Their 800-gallon seafood system crashed. Ammonia spiked to 3 ppm. Three lobsters dead. The service team was pulling their hair out.
I drove over. Looked at the sump. The filter was huge — enough for a 1,500-gallon system.
The problem? It was completely clogged. Nobody was cleaning it.
They had too much filtration for their maintenance capacity.
The First Mistake: Sizing by Glass
Here's what I see on almost every project.
Buyer spec says: "1,000-gallon tank. Need 1,000-gallon filtration."
That's wrong.
Two 1,000-gallon tanks can have completely different filtration needs.
| Tank | Fish Load | Ammonia Produced | Filtration Need |
|---|---|---|---|
| 1,000 gal, light stocking | Low | 0.5 ppm/day | 5x turnover |
| 1,000 gal, heavy seafood | High | 3-5 ppm/day | 10-15x turnover |
Same tank volume. 3x the filtration need.
Years ago I used to size filters by tank volume. I don't anymore.
The Second Mistake: Ignoring Maintenance Capacity
This is the one nobody talks about.
You can spec the perfect filter. If nobody cleans it, it fails.
I've seen systems with $10,000 in filtration that never worked — because the service team didn't have time to maintain them.
Here's the question buyers never ask:
Who cleans this? How often? How much time do they have?
That restaurant? The service team has 2 hours a week for the whole restaurant. They couldn't maintain that huge sump.
It clogged. The filter stopped working. Ammonia spiked.
The Bioload Math
Stop thinking in gallons. Start thinking in biomass.
Here's how I calculate it on every service call:
| Factor | What to Measure | Typical Range |
|---|---|---|
| Total fish weight | All fish in the system | 0.5-2 kg per 100 L |
| Feeding rate | kg of food per day | 1-3% of body weight |
| Desired turnover | Times per hour | 5x (light) to 15x (heavy) |
| Maintenance hours | Hours per week available | 2-20 hrs |
Heavy feeding = high ammonia = more filtration. Light feeding = low ammonia = less filtration.
That's the math that actually matters.
The Contradiction
Here's where I contradict myself.
Normally I recommend bigger filtration. Better safe than sorry. Over-sized filters have more buffer.
But this hotel? I told them to downsize.
Why? Because their maintenance team can't handle it. A smaller filter that gets cleaned every week works better than a huge filter that gets cleaned never.
That's the rule nobody teaches you:
The best filter is the one your team will actually maintain.
What I'm Not Going to Tell You
I can tell you how to calculate bioload. I can tell you the turnover rates. I can tell you the maintenance rule.
But I can't size your filter from "I have a 1,000-gallon tank." I don't know how many fish you're keeping. I don't know how much you're feeding. I don't know who's cleaning it.
That information comes from you.
What We Spec at Ruibit
When we design a system, we don't just ask "how big is the tank?"
We ask: "What are you keeping? How much are you feeding? Who's maintaining it? How often?"
Then we spec filtration that matches the bioload and the maintenance capacity.
The Hotel
That hotel restaurant?
We downsized the filter. Put in a smaller sump with easier access.
Now the service team cleans it every week.
Ammonia is stable. The lobsters are fine.
The best filter isn't the biggest one. It's the one that gets cleaned.
