Am I overfeeding?

[LJWilson]

In my new aquarium everything seems to generally be going ok but I appear to have a Diatom bloom that I cant keep away.
Regular testing shows my Nitrate levels to be about 2mg/L ( the lowest result my test kit will register) but I am not sure if this is a false reading caused by the Diatoms. I have a cloth bag containing phosphate absorber in one of the filter socks so phosphate reading is always zero. My pH holds steady at 8.3 which is where I want to be according to my LFS.

I only have two clowns and a royal Gramma at the mo and the tank has been running for about two and a half months and all the live rock is colouring nicely and I have no algae problems yet. I am feeding a quarter of a chunk of frozen food every other day and the chunks are about sugar cube size before I break them up. When I feed the fish all the food appears to be gone in seconds and what little the fish dont get my shrimp appear to be finishing before it hits the tank bottom.

Attached are some photos of my general set up but the tank size is 250l with around 150l in the sump. I have just stocked a refugium with some algae which is near enough on a counter cycle to the tank lights. I have a Nac 7 skimmer running 24/7.

Tank inhabitants apart from the fish are 4 corals, a sponge, two peppermint shrimp, two fire shrimp, six trochus snails and 4 hermit crabs.

Like I say the refugium has only just been stocked so not filled up the chamber yet so should I cut back on food or just wait for the plant life in the refugium to develop and hopefully remove any excess nitrate/nitrite?

 

[sjwitt]

Sounds like everything is fine. Tank looks great!

 

[uncleof6]

Silica would be the limiting factor for diatoms, rather than nitrates or phosphates. There is most likely a silica source (the water source or salt mix?) within the system. Once the silicates are used up, the diatom bloom will go away. You will see many blooms in your journey. Most are perfectly normal consequences of starting a system.

 

[LJWilson]

Im using tap water passed through a domestic RO filter. I have been doing regular changes of about 25l three times a week as this is the biggest water container I have and the filter takes about 8 hours to fill this.

 

[uncleof6]

I would try to upgrade your RO/DI unit. The makers of RO/DI units are very concerned about silica, and in some domestic water supplies, the level of silica is just too high. Silicon in one form or another is in a lot of food, but whether it is soluble or not is uncertain. Silica is contained in most salt mixes--whether they admit it or not--as well, though such depletes rather quickly.

Critters that can compete with diatoms for silica would be sponges, (second highest user of silica in the ocean,) and mollusks--though the mollusks probably get the silicon from eating diatoms. Some planktonic algae, radiolarians, and silicoflaggelates, also utilize silica. However, I would not expect any of these guys to do well, in a reef tank with silica levels kept artificially low, to control diatoms. Dosing, to encourage sponge survival, showed some disappointing results, usually a long slow death. Perhaps due to not dosing enough, or the source was not appropriate.

 

[dzfish17]

It sounds to me like you might be under feeding. I would feed that much at least once a day.

 

[aleonn]

You've got a nice tank! The rocks look a lot more mature than a 2.5 month tank

+1 on upgrading your RO/DI. I used to top off with my RO home unit but noticed lots of diatoms and pineapple sponges. Once I upgraded, the diatoms cleared up and the pineapple sponge population decreased (I still have a few around the rockwork).

 

[uncleof6]

You've got a nice tank! The rocks look a lot more mature than a 2.5 month tank

+1 on upgrading your RO/DI. I used to top off with my RO home unit but noticed lots of diatoms and pineapple sponges. Once I upgraded, the diatoms cleared up and the pineapple sponge population decreased (I still have a few around the rockwork).

The so called "pineapple sponge" generally lumped into the Genus Scypha within the hobby, are calcerous (Class: Calcarea) sponges, that could belong to the genera Scypha, Grantia, Sycon, Luecilla, or Luecandra. They all look the same. Their presence is unlikly to be affected by the silica levels, rather calcium carbonate.

The'silica using' sponges would be in the Class: Demospongiae, (demosponges.)

Specimens from within Class: Hexactinellida (glass sponges) will rarely be seen in the hobby.

 

[LJWilson]

Thanks for that advice everyone. I think I'll have to go back to getting water from LFS until I can upgrade my RO unit.

 

[zigzag1]

You just mention RO. Do you also have a DI stage? You can get them as add-ons to an existing system. JMTC & GL!