Hydrogen Peroxide Killed the BBA. It Also Killed Everything Else.

Hydrogen Peroxide Killed the BBA. It Also Killed Everything Else.

The BBA was gone. So was every beneficial bacterium in the tank. A planted tank hobbyist on r/PlantedTank went heavy on hydrogen peroxide to wipe out a persistent black brush algae outbreak — and it worked, in the most catastrophic way possible. The algae died. The biofilter, the invisible colony of bacteria that converts fish waste into something a tank can tolerate, died with it.

The recovery required a creative workaround: borrowing a canister filter from a separate established tank and running it on the crashed system for three days. That was enough to kick-start the nitrogen cycle. A week later, water parameters are testing clean, BBA is minimal, and the tank is — according to commenters — the best-looking it has ever been. One commenter called it "probably the best looking fish tank I've ever seen in my life," which is a remarkable outcome for a system that recently flatlined.

The lesson isn't that hydrogen peroxide is off the table — it's a recognized spot-treatment for algae. The lesson is that "more" is not "better," and a crashed biofilter is a far longer problem to solve than the algae you were trying to kill.

Gobble's Take: Your tank's bacteria are doing the hard, thankless work every single day — maybe don't nuke them in a panic over some ugly algae.

Source: r/PlantedTank

A Secret Reef Tank Survived Its Landlord Walkthrough. Barely.

The acros were too close together. The torches were too close to the acros. A rose bubble tip anemone had gone rogue, migrated up the rockwork, parked itself next to a zoa colony, and was now actively irritating it. By any objective measure, this reef tank had problems. And then the landlord walked in.

The outcome, shared to r/ReefTank, was not an eviction notice. The landlord inspected the undisclosed tank, decided it was "maintained enough," and let it stay. Commenters suspected the landlord will now use every future walkthrough as an excuse to come admire it — "free aquarium visit right there," as one put it. The reef keeper, meanwhile, is still trying to figure out how to relocate the wandering RBTA before it does any more diplomatic damage to the zoa neighborhood.

A well-kept tank apparently has a power that transcends lease agreements.

Gobble's Take: The best argument for keeping your reef immaculate isn't aesthetics — it's that your landlord might walk in at any moment.

Source: r/ReefTank

This Killifish from Nigeria's Niger Delta Grows to 6 Inches and Will Eat Anything That Fits in Its Mouth

The "Warri" Blue Gularis — Fundulopanchax sjoestedti — is one of the biggest killifish species you can keep, with males reaching 5 to 6 inches and females topping out around 4. It originates from Southern Nigeria's Niger Delta, carries iridescent coloring that prompted one commenter to call it "fancy with a capital F," and will, according to its keeper, eat bugs, crustaceans, and small fish without hesitation.

Unlike many killifish, the Blue Gularis is not an annual species — it can live up to three years in captivity. It prefers water temperatures between 72–78°F and a pH of 6 to 7.5. What it absolutely requires, non-negotiably, is a lid. These fish are exceptional jumpers, and at least one commenter learned that the hard way. They are also territorial, so tank size and space matter. The keeper behind this post calls it their all-time favorite fish — but also one that demands you think carefully before you buy.

Gobble's Take: A fish this stunning that can also leap out of an open tank and eat its neighbors is not a beginner fish — it's a commitment with fins.

Source: r/Aquariums

The Reef Fish That Licks Acropora Slime Instead of Eating the Polyps

The Orange Spotted Filefish (Oxymonacanthus longirostris) has a reputation that keeps most reef keepers from ever trying it. That reputation is not entirely wrong — but it is more complicated than the label "coral eater" suggests. One hobbyist keeping this species among acropora colonies explains what's actually happening: the fish uses its elongated, straw-like mouth not to consume polyps, but to remove the slime coating from Acropora surfaces. Healthy coral in a tank with plenty of colonies to browse experiences little real detriment, the keeper reports, though small frags cannot handle the extra attention.

The harder problem is feeding. These fish are specialized eaters and notoriously difficult to transition onto frozen food. The keeper notes they shouldn't be as readily available in the hobby as they currently are — because without the right setup, they struggle. In the right tank, though, a mature reef with abundant branching coral, they can thrive long-term. Unlike most corallivorous butterflies, which typically decline in captivity, this species can do genuinely well. The plan, if this one continues to thrive: add a mate and keep a pair.

Gobble's Take: A fish that licks coral slime for a living sounds manageable until you realize "manageable" requires a mature, heavily stocked reef and a lot of patience with a picky eater.

Source: r/ReefTank

Quick Hits

• First tank, first wins: A beginner shared their first planted tanks on r/PlantedTank — a 10-gallon they keep rearranging and a betta setup that commenters called "perfect" — with more plants already in the mail. r/PlantedTank
• Top-down Friday delivers: Reef keepers on r/ReefTank traded aerial shots of their systems, including a 14.5-gallon and a 2.5-gallon, both featuring rock flower anemones that are drawing serious envy in the comments. r/ReefTank

In Case You Missed It

Yesterday's top stories:

• The Inch-Per-Gallon Rule Has Been Wrecking Tanks for Decades
• A Vet's Blunt Diagnosis: Most Sick Fish Were Killed by Their Owner's Setup
• Thinking About Going Pro? Here's the Curriculum That Shows How Deep the Rabbit Hole Goes