Photo: Tommy Kronkvist · CC BY-SA 3.0
Gear
Aquarium root tabs for planted tanks
By Fishy Dave
Crypts, swords, and Vallisneria want food in the substrate. Push a root tab under the crown, not on top of the gravel. Liquid ferts are a different job for stem plants and epiphytes.
Food in the substrate, not only in the water
Root feeders pull nutrients through their roots. Cryptocoryne, Amazon swords, and Vallisneria belong in that group. On inert gravel or sand they stall without something under the crown. Root tabs put iron and other nutrients where those roots sit.
Liquid fertilizer is a different job. It feeds the water column for stem plants and for epiphytes like anubias and java fern. Easy to overdose. Our low-tech planted aquarium guide already names tabs under crypts. This page is the buying note.
How to place tabs so fish leave them alone
Push each tab midway into the substrate under or beside the plant crown. Seachem spacing is about one tab every 4 to 6 inches of planted bed. A typical 10-gallon needs about six tabs. Cover the hole so cories and diggers do not excavate a crumbly mess into the water.
Do not scatter tabs on top of the gravel. Do not crush a tab into the open water to "speed it up." Buried intact is the point. Nutrient aqua soil is a separate path with early ammonia leach. Test if you use soil. This page sticks to inert gravel or sand plus tabs.
Shrimp, fish, and what tabs will not fix
Buried modern tabs are fine in most community and shrimp tanks. Trouble shows up when a tab dissolves in open water or a digger brings one to the surface. Keep copper ich meds out of shrimp tanks. That warning is about medication, not about a buried Flourish tab.
Tabs will not fix ten hours of light with no timer. They will not replace weekly water changes. If the glass goes green, cut photoperiod and read the aquarium algae and LED light pages before you buy another bottle.
What to buy
The picks below are a 10-count Flourish Tabs pack for a 10- or 20-gallon bed, a 40-count of the same for a larger scape or multiple tanks, and optional Flourish Comprehensive liquid if you keep thirsty stem plants. Two of the three is enough for most low-tech tanks. We may earn a commission if you buy. See the affiliate disclosure.
What we would buy
Seachem Flourish Tabs, 10 count
The standard root-tab pack for a 10- or 20-gallon planted bed. Time-released tabs for the root zone under crypts and swords. Same 10-count we already point to from the low-tech planted guide.
One tab every 4 to 6 inches of planted substrate is the usual Seachem spacing. A typical 10-gallon bed needs about six tabs. Replace every few months as the maker directs. Skip burying tabs under anubias or java fern rhizomes. Those plants feed from the water.
See this listingSeachem Flourish Tabs, 40 count
Same formula in a multi-pack sized for a 29-gallon or larger scape, or for someone who redoses a few tanks. Cheaper per tab once you know you want Flourish under root feeders.
Still bury them. Do not dose forty tabs into one nano. Skip the big box if a single 10-count covers your one crypt cluster for the year.
See this listingSeachem Flourish Comprehensive, 250 ml
Optional liquid micros for stem plants and epiphytes that feed from the water column. Not a substitute for root tabs under crypts. Dose lightly. Overdoing liquid ferts is an easy way to feed hair algae.
Follow the bottle for a 10- or 20-gallon dose. Skip this pick if your tank is mostly crypts, swords, and Vallisneria on tabs with no thirsty stems. Keep copper meds out of shrimp tanks. Flourish itself is labeled shrimp-safe at normal doses when used as directed.
See this listing
Frequently asked questions
Do aquarium root tabs replace liquid fertilizer?+
No. Tabs feed plants that drink from the substrate. Liquid micros help stem plants and epiphytes that pull from the water. Many low-tech tanks run tabs alone for crypts and skip liquid until stems stall.
Where do I put root tabs in the tank?+
Push each tab midway into the gravel or sand under or next to the plant crown, about one tab every 4 to 6 inches of planted bed. Do not leave tabs on the surface where fish dig them up. Do not crush them into the water column.
Are root tabs safe for shrimp and fish?+
Most modern tabs are fine when buried in the substrate. Problems show up when tabs dissolve in open water or get smashed. Keep copper meds out of shrimp tanks separately. See the cherry shrimp and amano shrimp pages for copper warnings on meds.
How often should I replace root tabs?+
Follow the pack. Seachem Flourish Tabs are commonly redosed about every three to four months. API-style tabs often call for monthly adds. If new crypt leaves stay pale or melt after a settled period, check light and tabs before you dump a full liquid line.