If you look closely, you can see the tiny bladder traps that grow along the runners that make Utricularia graminifolia a carnivorous plant.
Utricularia graminifolia is a carnivorous plant originating in the tropical regions of Southeast Asia and India. It is a small sized aquarium plant with light green foliage and it is commonly used as a carpeting plant as it forms dense mats that creep across the substrate and hardscape. In stronger light its leaves grow no longer than an inch. However, if shaded or when receiving inadequate light, its leaves can elongate to be longer than an inch. It grows tiny bladders which trap tiny micro-organisms, which Utricularia graminifolia can digest for nutrients - these traps are too small to affect even shrimplets or baby fish. The plant takes awhile to acclimatize to the tank's environment, but once acclimatized, it grows quite quickly.
Utricularia graminifolia has a reputation for being a difficult aquarium plant, but this is primarily due to poor practices common in the aquarium hobby. (such as planting tissue culture plants in fresh aquasoil immediately after starting a new tank rather than planting after the tank has cycled). It has a few specific, but easily satisfied requirements - thereafter which Utricularia graminifolia is not a particularly demanding aquarium plant.
Utricularia graminifolia has a lighter green, almost yellowish green tone that contrasts well with plants with darker green tones. It is a fast spreading foreground plant once settled in. As it does not require substrate to grow well, it will creep up low-lying hardscape if given the chance.
The main requirement for growing Utricularia graminifolia is that it prefers to be planted in a matured and biologically stable tank system. Read this page on how tank maturity is defined. The tissue culture version of this plant is especially susceptible to melting in uncycled tanks. Generally, you will want to plant Utricularia graminifolia after the tank has cycled or has been running for a few weeks. You can start the tank growing other species of plants first. It has difficulty transitioning in newly set up or biologically unstable systems, especially tanks where ammonia spikes are common - if your Utricularia sample melts in the tank within days, it is most certainly due to this reason rather than anything else.
Utricularia graminifolia is a delicate plant and should be handled gently. Skill in handling the plant greatly increases success rates in getting it to settle in and grow. Be careful of breaking its delicate runners that connect the leaves together. Plant in smaller clumps in the substrate if you want to prevent the plant from floating up. Planting them well in the first try is important, as constant disturbance/up-rooting and replanting of clumps will damage the delicate plant. Clumps should be as small as possible without damaging the runner/leaf structure of the plant. To get a dense, healthy carpet, Carbon dioxide injection should be used. However, it can be grown as a floating plant in low tech/non Co2 injected setups as long as there is not too much flow. It can grow in warmer temperatures >26 Celsius, but will generally has looser form compared to growth in cooler temperatures. Poor light and overcrowded conditions give rise to elongated leaves.
Once planted in a certain spot, Utricularia graminifolia can take awhile to settle in. Tissue culture plants may take longer to settle in and transit compared to samples that were previously grown fully submerged. In this phrase, the plant can be quite vulnerable to algae, so having a stable tank that is not prone to algae attacks is helpful.
Due to tissue culture Utricularia graminifolia's proclivity for melting in new setups, there are various myths that surround its growth requirements, none of which are true. The two most common myths is that you have to grow it in nutrient poor water - that dosing fertilizers heavily will kill it, and that it needs soft water to grow. While the plant can be found often from soft water systems in the wild and its carnivorous adaptation allows it a competitive edge in nutrient poor systems, neither of these factors are required to grow it it well in the tank. It grows well in moderately hardwater and grows perfectly well in tanks that are heavily dosed with liquid fertilizers. Neither does it require a nutrient rich substrate to grow - it can grow perfectly well floating or on bare hardscape directly. Its runners will attach loosely to coarse hardscape such as lava rock over time.
Utricularia graminifolia can be used as an accent to give a different texture in the fore/mid ground. However, as the runners creep across terrain quickly, keeping it in place can be troublesome.
key success factors
Plant only in cycled tanks (preferably plant in tanks that has been running for 2-4 weeks already). Tissue culture is especially sensitive to melting if tank is not sufficiently matured
Overall tank stability and biological maturity matters more than anything else
Delicate plant requires careful handling, plant in fixed spot with minimal up rooting/disturbance
Not sensitive to the addition of fertilizers, so dosing should be done as it improves propagation rates
CO2 improves propagation and acclimatization rates significantly. Can be grow floating or in very shallow water in non CO2 tanks.
Submerged forms are much easier to handle for most hobbyists compared to the widely available tissue cultured versions
Pruning and propagation
Individual leaves are connected by a thin and delicate runner. Cutting off half a leaf and leaving behind a damaged half-leaf is an invitation for algae to infest. Utricularia graminifolia should be trimmed by dipping the scissors into the substrate and cutting the runners, then removing the connected leaves and runners completely so that there is minimal organic material left to rot.
With regards to carpeting plants such as UG, there are two main choices one can make.
1. Trim often, and trim deeply enough so that the existing carpet can renew itself. This entails trimming till some substrate is visible - and there is enough space for new growth to root well. Always aim to trim in the densest areas of growth. The downside of this method is that the carpet can (and should) look a bit thin after trimming and many less experienced aquarists are extremely hesitant to cut a carpet when it looks perfectly grown in. This method also requires much more regular work.
2. Wait for carpet to get really dense before doing a large trim. The risk of this is that bottom portions of the carpet would consist of very old growth that may be already deteriorating, and this can lead to most of the existing plant mass floating up. Another bad scenario that can happen is that most of the growth might be unhealthy due to over-crowding - leading to algae and other issues. This method often means that doing a large trim will probably entail some replanting of fresh top growth, after which the carpet will take longer to recover. The tank as a whole will go through a larger fluctuation with this method.
In summary, one has to choose between trimming lightly often, and trimming deeply (accompanied with some replanting) with less frequency.