Planet Zoo 2 aquariums: how to build one that works and keep it clean

If your first aquarium is empty, or full and somehow still not working, it’s not you. The game hands you a barrier tool and then quietly expects half a dozen other things, and it doesn’t always say which one is missing. Here’s the order I’d do it in, plus a short checklist for when it still misbehaves. (There’s one bit of number-crunching near the start that saves a lot of fiddling later.)

Pick the animals before you build

Two settings run the whole show. Salinity belongs to the filtration network, so every tank connected to it shares one water type. Temperature belongs to the individual tank. Your animals therefore decide what you need, and it’s worth a few minutes with the Zoopedia (the in-game animal encyclopedia) before you draw a single wall.

I went through the ranges for all 37 species, and a few things fall out of them. Twenty-eight need saltwater (a few of those also take brackish), eight are freshwater fish, and the manatee takes any water type. You’ll never be forced to use the brackish setting either, because every animal that accepts it also takes either fresh or salt.

Temperature is where it gets handy. Going by the listed ranges, 24 or 25°C is inside the range of all 29 animals that can live in saltwater, from the Ocean Sunfish (10 to 25°C) to the Javanese Cownose Ray (24 to 30°C). So for a saltwater tank, set it there and you don’t have to check each fish. Freshwater is messier, because the cool-water fish and the warm-water fish don’t overlap much.

Being in range only means the temperature isn’t hurting them. Who can actually share a tank is a separate question, and the Zoopedia lists it species by species (sharing a water type isn’t enough). One more cost tip: the bigger the gap between your set temperature and the weather outside, the more the tank costs to run, so lean towards whichever end of the range is closest to your local weather.

Space is the other thing that decides it. The cheapest animals to house are the Blackspotted Puffer, Red Lionfish and Clown Triggerfish, which need only 16 m² of deep water to start. Plenty of the small reef fish, like the Clown Anemonefish and Yellow Tang, start at 50 m². At the other end, the Great Hammerhead wants 960 m² and the Sand Tiger Shark 420 m² (plus 240 m² for each extra shark), so those are second-tank projects. Three animals come with the Deluxe Edition: the Great Hammerhead, the Longfin Batfish and the Blue and Gold Fusilier.

Building it

1. Flatten the ground, open Habitat Barriers and switch to the Aquarium tab. The ordinary habitat set isn’t the one you want.
2. Draw one closed loop. Glass suits most designs, and a gap anywhere means it isn’t a tank.
3. Stick an Aquarium Staff Gate on one of the walls. The tank fills as soon as it’s in, with fresh water to start. A normal Habitat Staff Gate won’t do this, which is an easy way to end up with a finished tank sitting empty.
4. Connect the gate to your paths, because staff can’t clean what they can’t reach.
5. Place a Water Filter near the tank (Facilities, then Utilities, or Add Filtration at the bottom of the aquarium’s panel) and make sure a generator reaches it.
6. Select the filter, pick Edit Filtration Network and drag its line to the gate. Choose Freshwater, Brackish or Saltwater on the same screen.
7. Open Environment on the aquarium’s panel and set the temperature. Then add feeders, nests and enrichment from the Aquarium tab, and only then the animals.

Make the walls higher than feels right. The water comes up to the gate at the very least, and since staff dive in wearing suits, the gate can sit well off the floor, which is a gift for deep tanks.

Do the salinity before the first fish goes in. New tanks start as fresh water, and a saltwater species won’t survive in it.

The three places it goes wrong

Nearly every “my filter does nothing” story ends in the same place. The filter links to the gate itself, on a little node that belongs to it. The glass doesn’t have one, so clicking around the walls gets you nowhere. A tank can be completely full and still show a “No Connected Water Filter” warning, which is the same problem in a different coat.

After that it’s a numbers game. The filter’s Filtration Rate has to at least match what the tank demands, and demand grows with the size of the tank and with every animal you add. A setup that was fine for an empty tank can slip later on. When the rate dips under demand, Water Cleanliness drifts down, and it recovers by itself once you’re back above. I couldn’t find a figure for what each filter covers, so watch the numbers on the aquarium’s panel instead of guessing.

Power is the other usual suspect. A filter with no generator in range says “Not Powered” and won’t clean anything. Ordinary generators are the budget option. Wind and solar are pricier to build, but they reach further, cost nothing to run and help your Sustainability Rating (one of the four parts of Zoo Reputation, if you’re working towards the accreditation guide).

Then there’s the part more filters can’t fix. Water Cleanliness is the network’s job, but Tank Cleanliness belongs to your Keepers, who put on diving suits and go in to scrub. It drops over time whatever the filter is doing, and it drops faster when the water is dirty. So if the tank looks grubby and the water is fine, check that Keepers can walk to the gate before you buy another filter. If both numbers stay low, animals can fall ill and may need quarantine and a vet.

Barriers wear out as well. Mechanics look after them, and a neglected wall cracks and eventually leaks. That’s bad news twice over, because guests nearby run off and an inspector who finds a leak can call off the inspection and fine you. Give Mechanics a way in before it gets that far.

Shoals, sharks and the view

There are 37 species in all, which is 35 fish plus the hawksbill turtle and the manatee. Twenty-one are aquarium only and 16 can also go in an exhibit (the small glass display tanks). Most of the fish (21 species) live as shoals. A shoal is one group instead of hundreds of separate fish, so the game tracks welfare for the whole group. It tops up its own numbers rather than breeding, ignores genetics and can split as it grows. Contraception stops the split, and poor welfare for long enough shrinks it. Update 1.0.5 fixed shoals ignoring the extra space after you enlarge a tank.

The big animals are simulated one by one. Sharks spend a lot of time “window surfing”, which means tracing the walls to get long straight swims, so a big shark will be happier with a few long walls than a tank full of tight curves. (The blacktip reef shark has to keep swimming, while the leopard shark doesn’t.) The ocean sunfish drifts along the glass to look at your guests, which is as charming as it sounds. In Franchise the Great Hammerhead and Ocean Sunfish are Tier 5 animals, so the accreditation guide is worth a look before you plan a tank around either.

The guest gate is the fun part. Add one and you can run a walkway right through the tank so guests walk beneath the surface, even at several different heights in the same tank. One-way glass and curved walls work like they do on land, and you can change the water’s colour tone and the lighting through the staff gate. Deep and multi-storey builds are well supported, including tanks sunk into the ground.

Changing a tank later

A tank with water or animals in it can’t be reshaped, so do it in this order. Box the animals up, hit Drain Water (it sits under the aquarium’s panel) and the barrier tool is yours for the outline, the wall height or the ground below. Refill, then recheck filtration, salinity, temperature and power before the animals come back. Taking the staff gate off also stops the automatic fill while you rework things. Since every edit means emptying the tank, I’d build bigger than feels sensible.

If it still won’t work

Go through these in order, because the early ones cause most of the trouble.

1. Is it full? If not, it’s the wrong gate or a gap in the loop.
2. Is the filter linked to the gate’s node, rather than just sitting near the tank?
3. Is the filter powered? Look for the “Not Powered” warning.
4. Does the salinity match everything inside?
5. Is a temperature set, and is it inside every animal’s range? The setting needs a powered gate, and if it’s missing, unpause the game for a moment and look again. Land heaters beside the tank won’t change the water.
6. Is the Filtration Rate above demand?
7. Can Keepers and Mechanics reach the gate and the walls?

If the game freezes when you place the gate, that’s a known problem some players hit. Make sure you’re on the latest update, pause before placing it, or try it a little higher on the wall. In Career, the Nordic Fjords aquarium wants saltwater at 28°C, and if that task still shows as incomplete after you pick saltwater, it’s usually the filter’s power or its link to the gate.

Once it’s running, the money guide covers the cash for keeping it going, and the breeding guide is handy for the animals you’ll end up with spare. (Every species’ needs are in the habitat requirements table too.)