In the marine aquarium there are three main types of filtration that are essential to a clean and stable environment. They are mechanical, biological and chemical. There are many commercially available products that combine these in one unit, such as canister filters, power filters and trickle filters but most are not suitable for a marine planted aquarium. Many of these designs will become nutrient sinks in time and can release large amounts of nitrates and phosphates into the aquarium water. While flow-through filters may be beneficial for some heavily planted aquariums and even necessary, generally it will create conditions favorable for excessive, undesired micro algae growth without regular cleaning of filter material. Maintaining an aquarium with marine macro algae and plants is often a balancing act between controlling the buildup of nitrates and organic material and providing just enough for a healthy ecosystem.  

Mechanical Filtration

For the marine planted aquarium the use of some form of mechanical filtration is normally needed. Plant material in time will break down to form sediments that can become nutrient sinks over time, especially in smaller aquariums. Some of this organic material will break down and be consumed by both macro algae and sea grasses but will also encourage micro algae growth. Depending on the size of the system these include the use of foam filter pads, micron filters and sock filters. Filter material should be cleaned or replaced often as they get dirty quickly in marine plant dominated systems. Protein Skimmers are very efficient at removing organic material and can be used in large systems that have a substantial bio-load. Some models are better than others, but most available today will produce good results. Overskimming can remove beneficial organisms, so running a skimmer continuously in a marine planted tank is not desirable as it will remove too many nutrients that the plants need to grow.

Biological Filtration

The best form of biological filtration for any marine system is the use of live rock or coral rubble. Live rock is full of organisms and bacteria that naturally filter aquarium water by consuming and converting nutrients and breaking down harmful elements through denitrification. Live rock is natural, attractive and provides a surface for marine plants to anchor and thrive. Uncured live rock is the best choice if it is cured properly because it will contain much more life than cured live rock. Aqua cultured live rock, although sometimes more dense than wildly collected rock, offers the hobbyist with the most variety of marine life, including beneficial bacteria, invertebrates and macro algae. External or internal pumps provide water circulation which is important for live rock to function. The size of the system and its inhabitants will dictate how much flow is ultimately needed.

Chemical Filtration

Photo by John LowtherThere are three main types of chemical media that are used to filter aquarium water. They are activated carbon, phosphate absorbing, and nitrate absorbing media. The use of activated carbon to chemically filter aquarium water has long been the preferred choice in both fresh and salt water aquariums. Although it can be useful in a marine planted aquarium, carbon should be used sparingly as it also can remove needed compounds and nutrients from the aquarium water. Phosphate and nitrate removing media can be used when levels get out of control but should be removed at the recommended interval so that the nutrients do not leach back into the aquarium after they have out lived their ability to absorb nutrients. A deep sand bed can also be utilized in a planted tank to control the amount of nitrate through the formation of anaerobic bacteria deep within the sand bed. Most deep sand beds need to be 6" or so to be effective however as too little depth can create a toxic mess. Overall nitrate is needed by all marine plants and depending on the rate of growth its presence in low levels is beneficial to the health of the system.

Botyocladia Sp.Aquarium water for use with a marine aquarium is made by dissolving salt mix with either purified water or tap water. The composition of household tap water varies greatly depending on what region the hobbyist resides. Tap water can be hard or soft, alkaline or acidic and contain variable amounts of other elements. Most salt mixes in the industry are composed of all naturally occurring elements found in natural seawater. Purified water is the best choice for any marine system as it removes 99% of contaminants and nutrients from the water. Sources of purified water include demineralized, reverse osmosis/deionization, and distilled water. In some cases tap water can be treated chemically and used in a marine planted aquarium. This is done with large scale aquaculture as the excess nutrients are quickly consumed by the plants. For most aquariums, purified water is the best choice and will help to drastically reduce unwanted algae blooms and harmful elements. If you live near the ocean, natural seawater can  be used, but can often add unwanted bacteria, pathogens and free floating algae to an aquarium if not treated. This can cause problems long term. Water changes are very important when maintaining a marine planted aquarium and help to remove nutrient rich water and replenish elements lost that were absorbed by the plants. The buildup of sediment on several species of macro algae such as Botryocladia (pictured) can be avoided by regular water changes, increased flow and mechanical filtration methods.


Natural seawater has a PH of 8.4. While most marine plants and organisms can survive in a wide range, it is best to strive to maintain a level as close as possible to natural conditions. An elevated ph can help reduce the growth of certain micro algae as many prefer a more acidic environment. 


Alkalinity is the measurement of water's ability to neutralize acids. The alkalinity of sea water keeps ph stable and a drop in alkalinity will lead to an eventual drop in ph. Most aragonite sand and salt mixes are sufficient to properly buffer aquarium water containing primarily marine plants. Again, water changes are essential for optimal health in any marine aquarium.


Most tropical species of marine plants can survive in a wide range of temperatures from about 72 degrees to 86 degrees. Some species found in both tropical and sub tropical environments grow in seasons however and have a distinct preference for certain water temperatures. The green macro algae Ulva is one such algae that prefers cooler water temperatures and will not survive long in any aquarium above 80 degrees. Sea grasses begin a dormant stage when the water temperatures are in the low to mid 60's and although remain alive, they will not grow. In the marine aquarium a range of 76 to 80 degrees is acceptable and should not present any problems for most tropical and sub tropical macro algae and sea grasses.


Photo by John LowtherSlight differences in salinity or specific gravity has no negative effect on the photosynthesis and growth of marine  plants. Many varieties of sea grass can adapt to very large swings in salinity in their natural environment. The change however, must be gradual, as a drastic change in salinity can cause most marine macro algae to undergo the process known as sporulation. When adding fresh water to an aquarium containing marine plants, especially Caulerpa, be careful not to change the overall salinity of the tank too quickly. Specific gravity levels in a marine aquarium are normally 1.024 - 1.026, but marine plants can survive in slightly higher ranges if desired. 


Water Circulation

The ocean is a dynamic and constantly changing environment, currents, tides and storms produce enormous amounts of exposure to plants, coral and fish. Water movement is very important for the growth of all marine plants in the aquarium. It aids in the removal of sediment, prevents some epithetic growth and provides increased diffusion of nutrients. Species such as Halymenia greatly benefit from strong flow to maintain their slippery fleshy fronds. How much flow is needed depends on the size of the system, but in general most plants can handle large amounts of movement.

Copyright 2010 GCE All rights reserved. No part of this online publication may be reproduced in any form by any means without the expressed permission of the author. All images are the property of Gulf Coast Ecosystems unless otherwise noted and should not be reproduced or distributed without permission.

Lighting for Marine Plants

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Nutrient Dosing